Placing flicky spawns in activation radius of a player start on spawn makes the game crash

tmthing set crash

This indicates that tmthing was set outside of the main level gamelogic code at P_Ticker and never properly cleared. ...I think

added SRB2Internal~11 label

mentioned in merge request !878 (closed)

mentioned in merge request !1522 (merged)

closed via merge request !1522 (merged)

mentioned in commit 69b6c409