Game Crash Fixes & Enhanced Stability

Bugfixes

• Fixed CTD related to region effect filtering out all provinces due to triggers.
• Fixed CTD related to having trade centers as tributaries.
• Fixed CTD fix related to the zone of control tooltips.
• Fixed CTD related to tool tipping a subunit that doesn't belong to a unit.
• Fixed CTD when missing to specify a modifier for opinion effect.
• Fixed CTD related to removing countries from the war which would invalidate paths due to forts blocking.
• Fixed CTD related to declaring war and subjects not having a subject type.