Crab king bumpers will sometimes break instantly when fighting crab king

This happens for me reliably if my boat is next to the ice when it breaks (ie, ice tile turns into boat_ice_crabking)

This can affect other structures on the boat as well. Just had my ice box and salt box destroyed by this bug.

I think this bug is in `oceanicemanager:DestroyIceAtPoint`. There's a check in there that structures aren't on an adjacent tile (L348), but I don't see a check for the entity being on a boat. As a result, any structures within the tile overhang will be removed.