Clean up shop.c

include/constants/items.h

@@ -477,7 +477,10 @@
 #define ITEM_OLD_SEA_MAP 376
 
 #define ITEMS_COUNT 377
-#define ITEM_FIELD_ARROW ITEMS_COUNT
+
+// A special item id associated with "Cancel"/"Exit" etc. in a list of items or decorations
+// Its icon is defined at ITEMS_COUNT as the "return to field" arrow
+#define ITEM_LIST_END 0xFFFF
 
 // Range of berries given out by various NPCS
 #define FIRST_BERRY_MASTER_BERRY      ITEM_POMEG_BERRY