Failed to call hook OnCollectiblePickup

This error always occurs

(23:20:18) | Failed to call hook 'OnCollectiblePickup' on plugin 'SimplePVE v1.2.6' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.SimplePVEExtensionMethods.ExtensionMethods.ForEach[T] (System.Collections.Generic.IEnumerable`1[T] source, System.Action`1[T] action) [0x00000] in <0431ba2412ad4079b4bf618d85ba933c>:0 
  at Oxide.Plugins.SimplePVE.OnCollectiblePickup (CollectibleEntity collectible, BasePlayer basePlayer) [0x00036] in <0431ba2412ad4079b4bf618d85ba933c>:0 
  at Oxide.Plugins.SimplePVE.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x032b0] in <0431ba2412ad4079b4bf618d85ba933c>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <206a0f2c6ee141f38e2ad549cde44d70>: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