Ok thanks, yes this is with the latest version.
I have no more information, than this.
And when i got this error in the Unity Editor, and if i press the Play button (Game paused on Error), after this i can play.
I got this error three times, when i join a game.
But what i noticed is, after i import the
Realistic FPS Prefab(The Realistic FPS Prefab is not synced, yet), i got this error, but if i disable all scripts, the error is still there.