Failed to call hook 'OnEntityTakeDamage'

Hi there, Im getting this in my console. not sure if its a bug or something.

Failed to call hook 'OnEntityTakeDamage' on plugin 'PlayerRanks v2.1.7' (KeyNotFoundException: The given key was not present in the dictionary.) at System.Collections.Generic.Dictionary`2[TKey,TValue].get_Item (TKey key) [0x0001e] in :0 at Oxide.Plugins.PlayerRanks.IsTeamMate (System.UInt64 playerID, System.UInt64 friendID) [0x00005] in <571ed0d237c0419ca6385b1cecdcf1e0>:0 at Oxide.Plugins.PlayerRanks.FriendCheck (BasePlayer player, BasePlayer victim) [0x00115] in <571ed0d237c0419ca6385b1cecdcf1e0>:0 at Oxide.Plugins.PlayerRanks.OnEntityTakeDamage (BaseEntity entity, HitInfo hitinfo) [0x0025b] in <571ed0d237c0419ca6385b1cecdcf1e0>:0 at Oxide.Plugins.PlayerRanks.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x008ea] in <571ed0d237c0419ca6385b1cecdcf1e0>:0 at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <31122a27a2414cd799150f8677cf39d4>:0 at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <0fbce81d88d64454b3e7abb24df7026b>:0 at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <0fbce81d88d64454b3e7abb24df7026b>:0