add a couple of onGearDamage callbacks to mine/barrel fall damage
Add nil checks on HHGear to rope steps.
aaaand where it was actually crashing
just in case. one more nil check
Issue 871 in hedgewars: "Hedgehog dropping into water while still attached to a rope makes engine crash"
Due to doStepRopeWork's being completely skipped 75% of the ticks - including drowning/detachment-condition checks
merge'n'magic