Failed to call hook....

Hi!
This have bothered me for a while now.
Appears when challenges are active. This error is from boar challenge.

Failed to call hook 'OnEntityKill' on plugin 'CustomChallenges v1.5.1' (NullReferenceException: Object reference not set to an instance of an object.)
  at Oxide.Plugins.CustomChallenges.OnEntityKill (BaseNetworkable Entity) [0x0000a] in <70b3636cda3f4f8ab43df5fac4235e04>:0 
  at Oxide.Plugins.CustomChallenges.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x0034c] in <70b3636cda3f4f8ab43df5fac4235e04>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <9c80d821d00a44c9a24497c73ad2d20d>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000de] in <d646191a355d43a6b3ab36b7ee14c740>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <d646191a355d43a6b3ab36b7ee14c740>:0 

Have edited the .cs file and added the item id for blood instead of the default item rewards since i cannot do that in the config.

Second thing: When players complete raidable bases, they often get boar or bear kill registered  in the scoreboard without killing any.
Its also possible to get Bear kill by destroying a Bear Rug.

Last thing: Could you add support for killing Chickens and Stags and picking up the new SunFlower, Orchid, Roses and Wheat?
Tried to add them to the config but didnt work.

CustomChallenges.json

Hello, as soon as i have some time, i will take a look on it.