Problem with the UI

Hey,

So I'm trying to set my trader with the UI in-game but it's not letting me add items for the "For Sale" and "Cost" sections. 
The UI works and I can search for the items, but when I press the new item and fill the text box of the Skin ID or amount, it does not replace the default item with the new item.

I would appreciate a fix, please.

I have also an error in the console, this is the error:

Failed to call hook 'cmdConsoleNPCS_UI' on plugin 'NPCShop v2.1.0' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.NPCShop.ShowUILots (BasePlayer player, System.UInt64 ID) [0x00123] in <5897e3d7966f42fc9ade98f4c786eed3>:0 03 ents, 0 slprs                                                                              2kb/s in, 9kb/s out
  at Oxide.Plugins.NPCShop.ShowUIMenu (BasePlayer player, System.UInt64 ID) [0x001c2] in <5897e3d7966f42fc9ade98f4c786eed3>:0
  at Oxide.Plugins.NPCShop.cmdConsoleNPCS_UI (ConsoleSystem+Arg arg) [0x009c9] in <5897e3d7966f42fc9ade98f4c786eed3>:0
  at Oxide.Plugins.NPCShop.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00655] in <5897e3d7966f42fc9ade98f4c786eed3>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <cd9a02fd331347bd82d550bb1a9c8e9f>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <b76ec77c47d1449e92b2baab8603843d>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <b76ec77c47d1449e92b2baaFailed to call hook 'cmdConsoleNPCS_UI' on plugin 'NPCShop v2.1.0' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.NPCShop.ShowUILots (BasePlayer player, System.UInt64 ID) [0x00123] in <5897e3d7966f42fc9ade98f4c786eed3>:0 03 ents, 0 slprs                                                                              1kb/s in, 9kb/s out
  at Oxide.Plugins.NPCShop.ShowUIMenu (BasePlayer player, System.UInt64 ID) [0x001c2] in <5897e3d7966f42fc9ade98f4c786eed3>:0
  at Oxide.Plugins.NPCShop.cmdConsoleNPCS_UI (ConsoleSystem+Arg arg) [0x009c9] in <5897e3d7966f42fc9ade98f4c786eed3>:0
  at Oxide.Plugins.NPCShop.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00655] in <5897e3d7966f42fc9ade98f4c786eed3>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <cd9a02fd331347bd82d550bb1a9c8e9f>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <b76ec77c47d1449e92b2baab8603843d>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <b76ec77c47d1449e92b2baa             

Changed Status from Pending to Work in Progress

Changed Status from Work in Progress to Closed

Changed Fixed In to 2.1.1