Hey guys. My friends minecraft has been crashing ever since yesterday. He has been playing this world for ages and using the same number of mods the same time.
Do you guys know why its crashing and how to fix it?

---- Minecraft Crash Report ----
// Don't do that.

Time: 15/06/14 21:43
Description: Ticking player

java.lang.ArrayIndexOutOfBoundsException: -24
at net.minecraft.potion.PotionEffect.func_76455_a(PotionEffect.java:186)
at net.minecraft.entity.EntityLivingBase.func_70679_bo(EntityLivingBase.java:605)
at net.minecraft.entity.EntityLivingBase.func_70030_z(EntityLivingBase.java:362)
at net.minecraft.entity.Entity.func_70071_h_(Entity.java:438)
at net.minecraft.entity.EntityLivingBase.func_70071_h_(EntityLivingBase.java:1781)
at net.minecraft.entity.player.EntityPlayer.func_70071_h_(EntityPlayer.java:342)
at net.minecraft.entity.player.EntityPlayerMP.func_71127_g(EntityPlayerMP.java:404)
at net.minecraft.network.NetServerHandler.func_72498_a(NetServerHandler.java:304)
at net.minecraft.network.packet.Packet10Flying.func_73279_a(SourceFile:136)
at net.minecraft.network.MemoryConnection.func_74428_b(MemoryConnection.java:89)
at net.minecraft.network.NetServerHandler.func_72570_d(NetServerHandler.java:141)
at net.minecraft.network.NetworkListenThread.func_71747_b(NetworkListenThread.java:54)
at net.minecraft.server.integrated.IntegratedServerListenThread.func_71747_b(IntegratedServerListenThread.java:109)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:691)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:175)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)


A detailed walkthrough of the error, its code path and all known details is as follows:
---------------------------------------------------------------------------------------

-- Head --
Stacktrace:
at net.minecraft.potion.PotionEffect.func_76455_a(PotionEffect.java:186)
at net.minecraft.entity.EntityLivingBase.func_70679_bo(EntityLivingBase.java:605)
at net.minecraft.entity.EntityLivingBase.func_70030_z(EntityLivingBase.java:362)
at net.minecraft.entity.Entity.func_70071_h_(Entity.java:438)
at net.minecraft.entity.EntityLivingBase.func_70071_h_(EntityLivingBase.java:1781)
at net.minecraft.entity.player.EntityPlayer.func_70071_h_(EntityPlayer.java:342)

-- Player being ticked --
Details:
Entity Type: null (net.minecraft.entity.player.EntityPlayerMP)
Entity ID: 182
Entity Name: EletricDragon
Entity's Exact location: 81.29, 64.00, 262.68
Entity's Block location: World: (81,64,262), Chunk: (at 1,4,6 in 5,16; contains blocks 80,0,256 to 95,255,271), Region: (0,0; contains chunks 0,0 to 31,31, blocks 0,0,0 to 511,255,511)
Entity's Momentum: 0.00, -0.08, 0.00
Stacktrace:
at net.minecraft.entity.player.EntityPlayerMP.func_71127_g(EntityPlayerMP.java:404)
at net.minecraft.network.NetServerHandler.func_72498_a(NetServerHandler.java:304)
at net.minecraft.network.packet.Packet10Flying.func_73279_a(SourceFile:136)
at net.minecraft.network.MemoryConnection.func_74428_b(MemoryConnection.java:89)
at net.minecraft.network.NetServerHandler.func_72570_d(NetServerHandler.java:141)

-- Ticking connection --
Details:
Connection: net.minecraft.network.NetServerHandler@17031c9
Stacktrace:
at net.minecraft.network.NetworkListenThread.func_71747_b(NetworkListenThread.java:54)
at net.minecraft.server.integrated.IntegratedServerListenThread.func_71747_b(IntegratedServerListenThread.java:109)
at net.minecraft.server.MinecraftServer.func_71190_q(MinecraftServer.java:691)
at net.minecraft.server.MinecraftServer.func_71217_p(MinecraftServer.java:587)
at net.minecraft.server.integrated.IntegratedServer.func_71217_p(IntegratedServer.java:175)
at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:484)
at net.minecraft.server.ThreadMinecraftServer.run(SourceFile:583)

-- System Details --
Details:
Minecraft Version: 1.6.4
Operating System: Windows 7 (x86) version 6.1
Java Version: 1.7.0_55, Oracle Corporation
Java VM Version: Java HotSpot(TM) Client VM (mixed mode, sharing), Oracle Corporation
Memory: 227945856 bytes (217 MB) / 512905216 bytes (489 MB) up to 518979584 bytes (494 MB)
JVM Flags: 2 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx512M
AABB Pool Size: 2307 (129192 bytes; 0 MB) allocated, 2196 (122976 bytes; 0 MB) used
Suspicious classes: FML and Forge are installed
IntCache: cache: 18, tcache: 0, allocated: 6, tallocated: 62
FML: MCP v8.11 FML v6.4.49.965 Minecraft Forge 9.11.1.965 Optifine OptiFine_1.6.4_HD_U_C8 30 mods loaded, 30 mods active
mcp{8.09} [Minecraft Coder Pack] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
FML{6.4.49.965} [Forge Mod Loader] (minecraftforge-9.11.1.965.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Forge{9.11.1.965} [Minecraft Forge] (minecraftforge-9.11.1.965.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
monnef-core{0.6.3} [monnef Core] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
SPCForge{1.1} [SPC Forge] (minecraft.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
LumberJack{1.6.4b} [LumberJack] ([1.6.4][c][forge]LumberJack (1).zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
MoarFood{v3.5.0} [MoarFood] ([1.6.4]MoarFoodV4.2.1 (1).zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
cfm{3.2.9.2} [§6MrCrayfish's Furniture Mod] ([Forge]FurnitureModv3.2.9.2(1.6.4).zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BiblioCraft{1.5.5} [BiblioCraft] (BiblioCraft[v1.5.5].zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Core{4.2.2} [BuildCraft] (buildcraft-A-1.6.4-4.2.2.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Builders{4.2.2} [BC Builders] (buildcraft-A-1.6.4-4.2.2.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Energy{4.2.2} [BC Energy] (buildcraft-A-1.6.4-4.2.2.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Factory{4.2.2} [BC Factory] (buildcraft-A-1.6.4-4.2.2.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Transport{4.2.2} [BC Transport] (buildcraft-A-1.6.4-4.2.2.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
BuildCraft|Silicon{4.2.2} [BC Silicon] (buildcraft-A-1.6.4-4.2.2.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
customnpcs{1.6.4} [CustomNpcs] (CustomNPCs_1.6.2-1.6.4 (2).zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
eplus{1.16.5b} [Enchanting Plus] (EnchantingPlus-1.16.5.zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
ExtrabiomesXL{3.15.8} [ExtrabiomesXL] (ExtrabiomesXL-universal-1.6.4-3.15.8 (1).jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
iChunUtil{2.3.0} [iChunUtil] (iChunUtil2.3.0.zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
IronChest{5.4.1.702} [Iron Chest] (ironchest-universal-1.6.4-5.4.1.702.zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Jaffas{0.6.3} [Jaffas and more!] (jaffas_0.6.3d.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Jaffas-Trees{0.6.3} [Jaffas - Trees] (jaffas_0.6.3d.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Jaffas-Technic{0.6.3} [Jaffas - Technic] (jaffas_0.6.3d.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Jaffas-Power{0.6.3} [Jaffas - Power] (jaffas_0.6.3d.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Jaffas-Xmas{0.6.3} [Jaffas - Xmas] (jaffas_0.6.3d.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
mca{3.6.0} [Minecraft Comes Alive] (MCA-3.6.0_MC-1.6.4.zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
monnef-core-helper{0.6.3} [monnef Core ~] (monnef_core_0.6.3b.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
MoreSwordsMod{2.6.0} [More Swords Mod] (More Swords Mod 2.6.0 For 1.6.4.jar) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
PortalGun{2.0.1} [PortalGun] (PortalGun2.0.1.zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
mod_ZanMinimap{0.9.4} [Zan's Minimap] (ZansMinimap1.6.4.zip) Unloaded->Constructed->Pre-initialized->Initialized->Post-initialized->Available->Available->Available->Available
Profiler Position: N/A (disabled)
Vec3 Pool Size: 2161 (121016 bytes; 0 MB) allocated, 2161 (121016 bytes; 0 MB) used
Player Count: 1 / 8; [EntityPlayerMP['EletricDragon'/182, l='New World', x=81.29, y=64.00, z=262.68]]
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fml,forge'