Do you know what might cause this error

Failed to call hook 'OnServerSave' on plugin 'Sirens v2.2.0' (NullReferenceException: )
  at (wrapper managed-to-native) UnityEngine.Component.GetComponentFastPath(UnityEngine.Component,System.Type,intptr)
  at UnityEngine.Component.GetComponent[T] () [0x00021] in <f90b5d60566c42cc8b1d1412300b3616>:0
  at Oxide.Plugins.Sirens.OnServerSave () [0x0001f] in <5bd3625d82fa49e1b811a05413457590>:0
                                                                                                                               0b/s in, 0b/s out
  at Oxide.Plugins.Sirens.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00485] in <5bd3625d82fa49e1b811a05413457590>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <87ce9ac9776a48658bc55eae6debe38b>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <cd7231f30b444d86bc6cca8a53cdd2ea>:0

Hi there,

sadly I currently don't. But I will have a look.

Best regards
ZockiRR

Failed to call hook 'OnServerSave' on plugin 'Sirens v2.2.0' (NullReferenceException: )
  at (wrapper managed-to-native) UnityEngine.Component.GetComponentFastPath(UnityEngine.Component,System.Type,intptr)
  at UnityEngine.Component.GetComponent[T] () [0x00021] in <5f55adde392a4f559fa097c2225879c0>:0

  at Oxide.Plugins.Sirens.OnServerSave () [0x0001f] in <c92c80cf9d534120b400a3a773f57898>:0

  at Oxide.Plugins.Sirens.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x00485] in <c92c80cf9d534120b400a3a773f57898>:0

  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <795304323ac74a298b8ed190a1dfa739>:0

  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000de] in <beb2b64691c64e2b95b99491bd85442c>:0

  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <beb2b64691c64e2b95b99491bd85442c>:0

Hi again,
currently trying heavily to reproduce this. But it is not possible for me and I also don't see what could cause this.

Is this happening on every server save? Or on plugin reload? Or on server shutdown?
I need more input.

Thanks for the link, also. But this does not relate. The car radio breaking the sirens is an error on CarRadio side which is rather obvious in code.
CarRadio is in fact a complete copy of Sirens (which is fine given the MIT license) but with worsened code... So I don't see me fixing this.

The OnServerSave thing on the other hand is really strange and will try to identify the problem, but like I said... I need more input.

Greetings 
ZockiRR