fix: Increase quantity by 1 UOM when adding an item from the selector in POS

(cherry picked from commit bbab850135)

erpnext/selling/page/point_of_sale/pos_controller.js

@@ -556,7 +556,9 @@ erpnext.PointOfSale.Controller = class {
 			const item_row_exists = !$.isEmptyObject(item_row);
 
 			const from_selector = field === "qty" && value === "+1";
-			if (from_selector) value = flt(item_row.stock_qty) + flt(value);
+			if (from_selector) {
+				value = flt(item_row.qty) + 1; // increase qty by 1 UOM
+			}
 
 			if (item_row_exists) {
 				if (field === "qty") value = flt(value);