Fixes disposal gas mismanagement

code/modules/recycling/disposal.dm

@@ -345,9 +345,6 @@
 	if(stat & BROKEN)			// nothing can happen if broken
 		return
 
-	if(!air_contents) // Potentially causes a runtime otherwise (if this is really shitty, blame pete //Donkie)
-		air_contents = new()		// new empty gas resv.
-
 	flush_count++
 	if( flush_count >= flush_every_ticks )
 		if( contents.len )
@@ -412,9 +409,6 @@
 	if(wrapcheck == 1)
 		H.tomail = 1
 
-
-	air_contents = new()		// new empty gas resv.
-
 	sleep(10)
 	if(last_sound < world.time + 1)
 		playsound(src, 'sound/machines/disposalflush.ogg', 50, 0, 0)
@@ -423,7 +417,7 @@
 
 
 	H.init(src)	// copy the contents of disposer to holder
-
+	air_contents = new() // The holder just took our gas; replace it
 	H.start(src) // start the holder processing movement
 	flushing = 0
 	// now reset disposal state