Fixes a table runtime (#19985)

* fixes table runtimes

* ryan's suggestion

code/__DEFINES/is_helpers.dm

@@ -53,6 +53,8 @@
 
 #define isstorage(A) (istype(A, /obj/item/storage))
 
+#define isstack(I) (istype(I, /obj/item/stack))
+
 GLOBAL_LIST_INIT(pointed_types, typecacheof(list(
 	/obj/item/pen,
 	/obj/item/screwdriver,

code/game/objects/structures/table_frames.dm

@@ -27,7 +27,10 @@
 
 ///Try to make a table with the item used to attack. FALSE if you can't make a table and should attack. TRUE does not necessarily mean a table was made.
 /obj/structure/table_frame/proc/try_make_table(obj/item/stack/stack, mob/user)
-	if(!stack?.table_type)
+	if(!istype(stack))
+		return FALSE
+
+	if(!stack.table_type)
 		return FALSE
 
 	if(stack.get_amount() < 1)