Chem grenade fix

- Restored "steam" code to chem grenades to handle grenades that don't have any reagents in them that react i.e. water grenades. (I removed it thinking it was only in there for handling foam reagents, but it seems it has more uses.)
This splashes the surrounding area in whatever reagents were leftover in the grenade after all reactions have occurred.
Merge pull request #4437 from Loganbacca/bayfix

Chem grenade fix - again