Need Help w/ GroupManager!

My console is spamming this line:
[Server] SEVERE [Essentials] Permission System Error: GroupManager returned: null

Here's my config file for groups.yml:
# Group inheritance
#
# Any inherited groups prefixed with a g: are global groups
# and are inherited from the GlobalGroups.yml.
#
# Groups without the g: prefix are groups local to this world
# and are defined in the this groups.yml file.
#
# Local group inheritances define your promotion tree when using 'manpromote/mandemote'

groups:
Commoner:
default: true
permissions:
- factions.kit.halfplayer
- essentials.kick.notify
- factions.leave
- essentials.warp.list
- essentials.warps.PvP
- essentials.warps.Donate
- essentials.warps.Chaos
- essentials.warps.Wilderness
- essentials.tpaccept
- essentials.tpdeny
- essentials.delhome
- essentials.suicide
- essentials.me
- essentials.helpop
- essentials.balance
- essentials.balancetop
- essentials.pay
- essentials.afk
- essentials.sethome
- essentials.home
- essentials.spawn
- essentials.msg
- essentials.warp
- essentials.signs.use.repair
- essentials.signs.use.heal
- essentials.signs.use.warp
- essentials.tpa
- -ChestShop.shop.create
- autorank.leaderboard
- autorank.check
- essentials.signs.use.enchant
- automessage.receive.default
inheritance: []
info:
prefix: '&f[Commoner] &f'
build: true
suffix: ''
Squire:
default: false
permissions:
- factions.create
- essentials.warps.Market
- essentials.tpahere
- essentials.tpa
inheritance:
- Commoner
info:
prefix: '&a[Squire] &f'
build: true
suffix: ''
Knight:
default: false
permissions:
- factions.kit.fullplayer
inheritance:
- Squire
info:
prefix: '&b[Knight] &f'
build: true
suffix: ''
Reaver:
default: false
permissions: []
inheritance:
- Knight
info:
prefix: '&c[Reaver] &f'
build: true
suffix: ''
Hero:
default: false
permissions: []
inheritance:
- Reaver
info:
prefix: '&2[Hero] &f'
build: true
suffix: ''
Vassal:
default: false
permissions: []
inheritance:
- Hero
info:
prefix: '&3[Vassal] &f'
build: true
suffix: ''
Lord:
default: false
permissions: []
inheritance:
- Vassal
info:
prefix: '&9[Lord] &f'
build: true
suffix: ''
Legend:
default: false
permissions: []
inheritance:
- Lord
info:
prefix: '&6[Legend] &f'
build: true
suffix: ''
King:
default: false
permissions: []
inheritance:
- Legend
info:
prefix: '&4[King] &f'
build: true
suffix: ''
Emperor:
default: false
permissions: []
inheritance:
- Enforcer
info:
prefix: '&5[Emperor] &f'
build: true
suffix: ''

Help please!