I get this error, can anyone help me??

[10:48] [main/INFO] [GradleStart]: No arguments specified, assuming client.
[10:48] [main/INFO] [GradleStart]: Extra: []
[10:48] [main/INFO] [GradleStart]: Running with arguments: [--userProperties, {}, --assetsDir, C:/Users/Rowan/.gradle/caches/minecraft/assets, --assetIndex, 1.7.10, --accessToken, {REDACTED}, --version, 1.7.10, --tweakClass, cpw.mods.fml.common.launcher.FMLTweaker, --username, ForgeDevName]
[10:48] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLTweaker
[10:48] [main/INFO] [LaunchWrapper]: Using primary tweak class name cpw.mods.fml.common.launcher.FMLTweaker
[10:48] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLTweaker
[10:48] [main/INFO] [FML]: Forge Mod Loader version 7.10.18.1180 for Minecraft 1.7.10 loading
[10:48] [main/INFO] [FML]: Java is Java HotSpot(TM) 64-Bit Server VM, version 1.8.0_20, running on Windows 8.1:amd64:6.3, installed at C:\Program Files\Java\jre1.8.0_20
[10:48] [main/INFO] [FML]: Managed to load a deobfuscated Minecraft name- we are in a deobfuscated environment. Skipping runtime deobfuscation
[10:48] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
[10:48] [main/INFO] [LaunchWrapper]: Loading tweak class name cpw.mods.fml.common.launcher.FMLDeobfTweaker
[10:48] [main/INFO] [LaunchWrapper]: Calling tweak class cpw.mods.fml.common.launcher.FMLInjectionAndSortingTweaker
[10:48] [main/ERROR] [LaunchWrapper]: Unable to launch
java.util.ConcurrentModificationException
at java.util.ArrayList$Itr.checkForComodification(Unknown Source) ~[?:1.8.0_20]
at java.util.ArrayList$Itr.remove(Unknown Source) ~[?:1.8.0_20]
at net.minecraft.launchwrapper.Launch.launch(Launch.java:117) [launchwrapper-1.9.jar:?]
at net.minecraft.launchwrapper.Launch.main(Launch.java:28) [launchwrapper-1.9.jar:?]
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_20]
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_20]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) ~[?:1.8.0_20]
at java.lang.reflect.Method.invoke(Unknown Source) ~[?:1.8.0_20]
at GradleStart.bounce(GradleStart.java:107) [start/:?]
at GradleStart.startClient(GradleStart.java:100) [start/:?]
at GradleStart.main(GradleStart.java:55) [start/:?]
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0
at GradleStart.main(GradleStart.java:59)
Java HotSpot(TM) 64-Bit Server VM warning: Using incremental CMS is deprecated and will likely be removed in a future release