This is a small fix for that infamous "where are the shotblocks in Croc's room" bug.

It's caused by an overflow when a long beam (at least wave + plasma) goes offscreen above a room, out of bounds, and the top of the room starts at Y = 0. The beam overflows the shot block reaction routine when it gets the next index from the out of bounds block to the inside block.
It will actually happen in any room as long as you have a long beam, but you won't get a shotblock sound unless the blocks around the area use a tiledata value of $XX4X or $XXCX, which is not often.

This small ASM will make it so even if the shot overflows, it will never have an incorrect block index and always check the right blocks.
Free space is used from $94DFF7 -> $94DFFD.