Improved detection of 1 unit army spawns, fixing a potential crash.

Was a chance for battles relieving settlements to not be correctly identified, spawning a fort army. Fort armies now correctly do not spawn if you are relieving a settlement (fort already reinforces through game code).

Fort armies that were completely destroyed when reinforcing occassionaly were not identified properly. Now identified properly. If a reinforcing fort army is completely destroyed, it is also destroyed in the fort (units deleted, not set to 1hp).

Was a chance for battles over forts to not be correctly identified, spawning a fort army. Fort armies now correctly do not spawn if you are fighting over a fort.