I often began to observe this error.
[Oxide] 21:01 [Error] Failed to call hook 'CanDropActiveItem' on plugin 'RestoreUponDeath v0.3.7' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Core.Libraries.Permission.UserHasPermission (System.String id, System.String perm) [0x0000a] in <12678b905a6d43c3a9cc366104306651>:0
  at Oxide.Plugins.RestoreUponDeath.HasAnyPermission (System.String playerId) [0x00023] in <e46b47d09fd24147a655a8a5d98fdf06>:0
  at Oxide.Plugins.RestoreUponDeath.CanDropActiveItem (BasePlayer player) [0x00012] in <e46b47d09fd24147a655a8a5d98fdf06>:0
  at Oxide.Plugins.RestoreUponDeath.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x001d5] in <e46b47d09fd24147a655a8a5d98fdf06>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <60c318df79ed41688ea59335e48d61ad>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <12678b905a6d43c3a9cc366104306651>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <12678b905a6d43c3a9cc366104