Merge pull request #3244 from Citadel-Station-13/upstream-merge-31422

[MIRROR] Internals set to 0 pressure will properly prevent breathing environment air

code/modules/mob/living/carbon/life.dm

@@ -78,7 +78,7 @@
 		//Breathe from internal
 		breath = get_breath_from_internal(BREATH_VOLUME)
 
-		if(!breath)
+		if(isnull(breath)) //in case of 0 pressure internals
 
 			if(isobj(loc)) //Breathe from loc as object
 				var/obj/loc_as_obj = loc
@@ -226,7 +226,9 @@
 			update_internals_hud_icon(0)
 		else
 			update_internals_hud_icon(1)
-			return internal.remove_air_volume(volume_needed)
+			. = internal.remove_air_volume(volume_needed)
+			if(!.)
+				return FALSE //to differentiate between no internals and active, but empty internals
 
 /mob/living/carbon/proc/handle_blood()
 	return