Just found a bit of a bug, methinks. Sequence of actions:
Start new game.
Insert Sprite object, copy and paste clone of said object.
Now assign each object to the Blue and Friendly families (you can have both selected or do it one by one).
Now remove the Blue family from both objects (Say yes to the warning that it's the last Blue object).
Go into the event editor, start a new event - the (supposedly removed) Blue family is the only one available there.
Double Click it - it'll show up empty.
Now cancel - CC crashes.
Here's the cap. Just remove the Friendly family and go into event editor to add something.
I have replicated this four times, added to the bug tracker as well.