Typecheck all return_air calls (#15363)

code/game/objects/items/airbubble.dm

@@ -580,8 +580,7 @@
 /obj/structure/closet/airbubble/proc/get_turf_air()
 	var/turf/T = get_turf(src)
 	if(T)
-		. = T.return_air()
-	return
+		return T.return_air()
 
 /obj/structure/closet/airbubble/proc/return_pressure()
 	. = 0

code/game/objects/items/devices/scanners.dm

@@ -377,9 +377,9 @@ BREATH ANALYZER
 	origin_tech = list(TECH_MAGNET = 1, TECH_ENGINEERING = 1)
 
 /obj/item/device/analyzer/atmosanalyze(var/mob/user)
+	if(!user) return
 	var/air = user.return_air()
-	if (!air)
-		return
+	if (!air) return
 
 	return atmosanalyzer_scan(src, air, user)
 

code/game/objects/items/devices/suit_cooling.dm

@@ -84,7 +84,7 @@
 			return C.air_contents.temperature
 
 	var/turf/T = get_turf(src)
-	if(istype(T, /turf/space))
+	if(istype(T, /turf/space) || !isturf(T))
 		return FALSE	//space has no temperature, this just makes sure the cooling unit works in space
 
 	var/datum/gas_mixture/environment = T.return_air()

code/game/objects/objs.dm

@@ -101,8 +101,6 @@
 /obj/return_air()
 	if(loc)
 		return loc.return_air()
-	else
-		return null
 
 /obj/proc/updateUsrDialog()
 	if(in_use)

code/game/objects/structures/pit.dm

@@ -62,8 +62,6 @@
 /obj/structure/pit/return_air()
 	if(open && loc)
 		return loc.return_air()
-	else
-		return null
 
 /obj/structure/pit/proc/digout(mob/escapee)
 	var/breakout_time = 1 //2 minutes by default

code/game/objects/structures/transit_tubes.dm

@@ -366,6 +366,7 @@ obj/structure/ex_act(severity)
 //  giving it a chance to mix its internal air supply with the turf it is
 //  currently on.
 /obj/structure/transit_tube_pod/proc/mix_air()
+	if(!loc) return
 	var/datum/gas_mixture/environment = loc.return_air()
 
 	//note that share_ratio assumes both gas mixes have the same volume,