Stops airlocks from getting harddeleted, also fixes an unrelated runtime (#31412)

* Stops airlocks from getting harddeleted, also fixes an unrelated runtime

Destroying doors with a sniper rifle or anything that flat out destroys them good would runtime in doors.dm #L184.
Also doors would very often not get qdel'd properly, it was not 100% of the time but very common, this *seems* to fix it but since reproducing the bug was never quite certain, I'm not absolutely sure I got it. I did destroy all the doors on the station without triggering a harddel on a door after this fix, where previously it would happen.

* old friend ex_act

code/game/objects/obj_defense.dm

@@ -52,10 +52,12 @@
 		return
 	..() //contents explosion
 	if(target == src)
+		obj_integrity = 0
 		qdel(src)
 		return
 	switch(severity)
 		if(1)
+			obj_integrity = 0
 			qdel(src)
 		if(2)
 			take_damage(rand(100, 250), BRUTE, "bomb", 0)