oh boy

code/game/objects/buckling.dm

@@ -36,8 +36,7 @@
 
 //procs that handle the actual buckling and unbuckling
 /atom/movable/proc/buckle_mob(mob/living/M, force = FALSE, check_loc = TRUE)
-	if(!buckled_mobs)
-		buckled_mobs = list()
+	LAZYINITLIST(buckled_mobs)
 
 	if(!istype(M))
 		return FALSE

code/modules/mob/mob.dm

@@ -760,7 +760,7 @@ GLOBAL_VAR_INIT(exploit_warn_spam_prevention, 0)
 //You can buckle on mobs if you're next to them since most are dense
 /mob/buckle_mob(mob/living/M, force = FALSE, check_loc = TRUE)
 	if(M.buckled)
-		return 0
+		return FALSE
 	var/turf/T = get_turf(src)
 	if(M.loc != T)
 		var/old_density = density
@@ -768,7 +768,7 @@ GLOBAL_VAR_INIT(exploit_warn_spam_prevention, 0)
 		var/can_step = step_towards(M, T)
 		density = old_density
 		if(!can_step)
-			return 0
+			return FALSE
 	return ..()
 
 //Default buckling shift visual for mobs