Failed to call hook 'cmdBuyCommand' on plugin 'ServerRewards v0.4.71' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.ServerRewards.cmdBuyCommand (ConsoleSystem+Arg arg) [0x00057] in <cd7b7d48795a4216a5aa0eab75f512e1>:0
  at Oxide.Plugins.ServerRewards.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00e2a] in <cd7b7d48795a4216a5aa0eab75f512e1>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <70dc8de1abd4423db5f501c6845edf22>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <ac41dd3599754d448b8c218b34645820>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <ac41dd3599754d448b8c218b34645820>:0

May i know what is this problem? And how can i fix this issue.

@k1lly0u - I have been getting this same NRE on Kits, Commands and Items. Even with version 0.4.72

I have several NPCs (HumanNPC) setup as vendors via /srnpc, a few of which have commands as things that can be purchased. Since the Nov 5 update, purchasing those commands fails with:

Failed to call hook 'cmdBuyCommand' on plugin 'ServerRewards v0.4.73' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.ServerRewards.cmdBuyCommand (ConsoleSystem+Arg arg) [0x00057] in <6f9566c1d0c949c796a7555e9ff3c57e>:0 
  at Oxide.Plugins.ServerRewards.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00e2a] in <6f9566c1d0c949c796a7555e9ff3c57e>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <80b90e8213db44b29ec2d4111764172c>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in :0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in :0 

Merged post

I got merged into this thread. Any updates on this? Users can no longer buy minicopters and boats in my server w/ their Economic balance due to this error. For me, the NRE did not start occurring until Nov 5th update.

Merged post

@k1lly0u thank you for this amazing plugin. I really appreciate the hard work you've put into it. the above bug is fairly compromising in regards to my server's offerings. Is there any chance this NRE could be investigated? Thank you very much for your time.

This issue still persists, players are no longer able to buy items, kits, or commands from an NPC vendor (/srnpc) in ServerRewards.

purchasing items from NPCs on my server is still broken after several weeks due to this error. I desperately ask that someone, anyone, address this problem, please. As mentioned previously, the error began w/ the Nov 5 update for me, and has stripped away many of the interactive features of my server. If anyone has any idea how to resolve this issue, or even where to begin in potentially fixing the error, I would be exceptionally grateful for your time. Thank you.