Addresses #1660.

I'm not sure exactly how this happens, but this should stop the error
from causing a crash.
Blocs react to bats.
Merge pull request #1661 from Protuhj/fix_weapon_error_1660

Addresses #1660.
Merge pull request #1779 from DaNiwa/bat_fix

Blocs react to bats.
Merge branch 'master' into forestcave