Fix Slime runtime errors

Changes:
1) Checks if mobs actually have a heart organ before attempting to use it.
2) Checks if species_allowed exists before using it.
3) Minor map fixes. It didn't mapmerge properly, but seeing as my last changes already involved about 4,000 actual line changes, I presume it won't matter much. If it does, contact me and I'll re-do those changes.