Sudden Declaration of War

Hi everyone,
the headline might indicate it, but my problem seems to be a little bit more difficult. It seems like that my civilization suddenly declares war on ist own on another civilization during the processing of the turns of the other civilizations - quite annoying since I also have a declaration of friendship and a research agreement with them. Maybe I have an error which I don't see so if someone can help me I would be very grateful. Thanks in advance

The savegame is attached, latest patch Version with all DLCs and the Mod infoaddict (v. 22)

The attached file doesn't seem to work so here is a link because the savegame is bigger than the allowed 2 MB:

http://ul.to/uq0yzldv

You've got a Defensive Pact with Theadora, Alex declares war on her, so you declar war on him.

Thanks for the fast answer. I didn't even know I had one, nor remembered I made one. I feel quite supid now.