Somethingonplayer

If a slimer is currently attached to the player, this holds the slimer's sprite ID. Otherwise, this is -1.

To kill the slimer from code, we can't just apply htextra as we would expect, the correct way to kill a facehugging slimer is this:

    ifn player[].somethingonplayer -1
    {
        seta[player[].somethingonplayer].htextra 1
        seta[player[].somethingonplayer].htg_t 0 0
        setp[].somethingonplayer -1
    }