Tons of errors and after every server restart I have to delete player data file to fix

So I get tons of errors and after every server restart I have to delete player data file to get the custom buttons to be able to appear on screen again then reload the plugin. How can I fix?

Failed to call hook 'OnLootEntityEnd' on plugin 'CustomButtons v2.0.72' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.CustomButtons.ShowButtons (BasePlayer player) [0x00011] in <257f38ecb053473fa7218d4c595a3b4f>:0 
  at Oxide.Plugins.CustomButtons.OnLootEntityEnd (BasePlayer player, BaseEntity entity) [0x00000] in <257f38ecb053473fa7218d4c595a3b4f>:0 
  at Oxide.Plugins.CustomButtons.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00f11] in <257f38ecb053473fa7218d4c595a3b4f>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <42f9bedc659b4f4786eb778d3cd58968>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000de] in <d59b507fd76240e5b62228d0eae39b73>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <d59b507fd76240e5b62228d0eae39b73>:0