Quite simple actually, checks to make sure the brick is alive (Not destroyed) before launching the event.
EX: onbrickdestroy-self-firerelaynorth
Another brick: Onrelay-self-ifbrickalive
Varibletrue-self-setemitter-fire
Using this, you could make a wall of bricks, blow part of it up, and the remaining bricks by the part that got blown up would be on fire.
