Stops fire_act from trying to add the burning component to qdeleted atoms (#90125)

## About The Pull Request


![firefox_ofVVJ1vhpG](https://github.com/user-attachments/assets/5c01541f-acae-4173-bb13-6479b4ab1694)

Fixes this flaky runtime involving burning trash.

## Why It's Good For The Game

`take_damage()` destroying candy wrappers should not cause my CI to
fail. Go away.

code/game/objects/obj_defense.dm

@@ -133,6 +133,8 @@
 			return
 	if(exposed_temperature && !(resistance_flags & FIRE_PROOF))
 		take_damage(clamp(0.02 * exposed_temperature, 0, 20), BURN, FIRE, 0)
+	if(QDELETED(src)) // take_damage() can send our obj to an early grave, let's stop here if that happens
+		return
 	if(!(resistance_flags & ON_FIRE) && (resistance_flags & FLAMMABLE) && !(resistance_flags & FIRE_PROOF))
 		AddComponent(/datum/component/burning, custom_fire_overlay || GLOB.fire_overlay, burning_particles)
 		SEND_SIGNAL(src, COMSIG_ATOM_FIRE_ACT, exposed_temperature, exposed_volume)