[7.1] Idle biters

[Coolthulhu]

Some of the biters seem to be created without any script controlling them, just standing in place.
Biters will also sometimes return to roaming when their target is deconstructed, even if they're being attacked.

I've only tested those on a migrated 7.0 save, but the bugged biters were created after migration.

[kovarex]

Hello, this has been probably fixed, there were lot of ai fixes in 0.7.1 + 0.7.2