Getting tons of these errors causing server stalls after the latest May facepunch Update can you fix it?

Calling kill - but already IsDestroyed!? loot_barrel_2[0]
Failed to call hook 'OnEntityDeath' on plugin 'PlayerChallenges v2.0.52' (NullReferenceException: Object reference not set to an instance of an object.)
  at Oxide.Plugins.PlayerChallenges.OnEntityDeath (BaseCombatEntity entity, HitInfo info) [0x00352] in <96ab43f6f33b422cbfc22578a929f8e7>:0

  at Oxide.Plugins.PlayerChallenges.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00e88] in <96ab43f6f33b422cbfc22578a929f8e7>:0

  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <795304323ac74a298b8ed190a1dfa739>:0

  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000de] in <beb2b64691c64e2b95b99491bd85442c>:0

  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <beb2b64691c64e2b95b99491bd85442c>:0

Calling kill - but already IsDestroyed!? loot_barrel_2[0]