Minor refactor of how gas IDs are handled

code/modules/assembly/bomb.dm

@@ -107,8 +107,8 @@
 	return
 
 /obj/item/tank/proc/ignite()	//This happens when a bomb is told to explode
-	air_contents.assert_gases("plasma", "o2")
-	var/fuel_moles = air_contents.gases["plasma"][MOLES] + air_contents.gases["o2"][MOLES]/6
+	air_contents.assert_gases(/datum/gas/plasma, /datum/gas/oxygen)
+	var/fuel_moles = air_contents.gases[/datum/gas/plasma][MOLES] + air_contents.gases[/datum/gas/oxygen][MOLES]/6
 	air_contents.garbage_collect()
 
 	var/strength = 1
@@ -164,4 +164,4 @@
 	if(!T)
 		return
 	T.assume_air(removed)
-	air_update_turf()
+	air_update_turf()