fixes an invisibility exploit (#16573)

code/modules/vehicles/rover_vr.dm

@@ -292,12 +292,15 @@
 	if(!istype(C, /mob/living/carbon/human))
 		return 0
 
+	. = ..(C)
+
+	if(!.)
+		return
+
 	if(ismob(C))
 		buckle_mob(C)
 		C.alpha = 0
 
-	return ..()
-
 /obj/vehicle/train/rover/engine/unload(var/mob/user, var/direction)
 	var/mob/living/carbon/human/C = load
 

code/modules/vehicles/vehicle.dm

@@ -340,7 +340,7 @@
 			C.pixel_y += load_offset_y
 		C.layer = layer + 0.1
 
-	if(ismob(C))
+	if(ismob(C) && user)
 		user_buckle_mob(C, user)
 
 	return 1