I'm getting the following error message in console:

Failed to call hook 'API_TimeMute' on plugin 'BetterChatMute v1.2.1' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.BetterChatMute.API_TimeMute (Oxide.Core.Libraries.Covalence.IPlayer target, Oxide.Core.Libraries.Covalence.IPlayer player, System.TimeSpan timeSpan, System.String reason, System.Boolean callHook, System.Boolean broadcast) [0x00000] in <13c72f79473e4a74b2f70105bc85594f>:0

  at Oxide.Plugins.BetterChatMute.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00373] in <13c72f79473e4a74b2f70105bc85594f>:0

  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <23ba99f131254889867c71f0bd137b1d>:0

  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <157a94ee66ab4a7991faecd1eb84be3b>:0

  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <157a94ee66ab4a7991faecd1eb84be3b>:0