Failed to call hook 'OnPlayerDisconnected' on plugin 'Bounty v0.2.6' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.Bounty.OnPlayerDisconnected (BasePlayer player) [0x00000] in <50f26d4852d940e99f35a6907cbd4aeb>:0 
  at Oxide.Plugins.Bounty.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x002b7] in <50f26d4852d940e99f35a6907cbd4aeb>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <8a646463979e4a1d9c0e2f1298e9483f>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <1fe782f4b27a43ae85d29ebb2d56c007>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <1fe782f4b27a43ae85d29ebb2d56c007>:0 

This is one example, but im getting it on most hooks. OnServerInitialized cmdBounty

Plugin error on connect

Failed to call hook 'OnPlayerConnected' on plugin 'Bounty v0.2.6' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.Bounty.OnPlayerConnected (BasePlayer player) [0x00000] in <043827f962aa43d8bc2573e41b269f0a>:0

  at Oxide.Plugins.Bounty.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x0028c] in <043827f962aa43d8bc2573e41b269f0a>: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 <50629aa0e75d4126b345d8d9d64da28d>:0

  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <50629aa0e75d4126b345d8d9d64da28d>:0

Failed to call hook 'OnPlayerDisconnected' on plugin 'Bounty v0.2.6' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.Bounty.OnPlayerDisconnected (BasePlayer player) [0x00000] in <043827f962aa43d8bc2573e41b269f0a>:0

  at Oxide.Plugins.Bounty.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x002b7] in <043827f962aa43d8bc2573e41b269f0a>: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 <50629aa0e75d4126b345d8d9d64da28d>:0

  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <50629aa0e75d4126b345d8d9d64da28d>:0

Seeing a lot of errors myself since the last Rust update.

Merged post

Looks like I resolved it.  The data file was blank.  Deleteing it and the folder and reloading the plugin recreated the data file and it seems fine now.

Got this since a while. Same on disconnect.

Failed to call hook 'OnPlayerConnected' on plugin 'Bounty v0.2.6' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.Bounty.OnPlayerConnected (BasePlayer player) [0x00000] in <c4fccfa2a2f94b4d864dcc31a2ab9f16>:0
  at Oxide.Plugins.Bounty.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x0028c] in <c4fccfa2a2f94b4d864dcc31a2ab9f16>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <60c318df79ed41688ea59335e48d61ad>:0                                                                                                                                                                     6kb/s in, 35kb/s out
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <50629aa0e75d4126b345d8d9d64da28d>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <50629aa0e75d4126b345d8d9d64da28d>:0​

So the issue seems to be when the server wipes it's not recreating the data file correctly.  I'm having the same issue with the LandLord plugin.  But yeah, deleting the folder and file and then reloading the plugin solves the problem.