Diplomacy hit with ally and city state

So this bug is probably not very common, since it is a rather complicated setup.

I have a mutual defense pact with Portugal. Portugal is at war with Rome (but I am not), and has pledged to protect a neutral city state. Rome becomes allied to the city state, who then declares war on Portugal. I automatically declare war on the city state due to the mutual defense pact. Portugal is now mad at me for attacking a city state under their protection.

The bug may be triggered in more general circumstances, but this was my setup.

They just haven't implemented defense pacts really yet. They should disable them until they find a way to make them work.

Until then: Do not and never sign defense pacts.

Well, it's a shame because defensive pacts are potentially a good way to get otherwise friendly civs to declare war on each other.