I keep getting attacked by protectorates. I try to use protectorates to help manage empires. However as often as not I will be attacked by one (50/50) . In my last game I was attacked by a protectorate who aside from me had no allies and no enemies and just to be sure I checked after the attack and they only had me as an enemy and no allies.

Is this just another fun bug to add to the protectorate status or does anyone here know what is happening?