fix(购物车)：库存不足时尺寸修改

 {
   "name": "yohobuywap-node",
-  "version": "6.12.5",
+  "version": "6.12.6",
   "private": true,
   "description": "A New Yohobuy Project With Express",
   "repository": {

@@ -154,7 +154,7 @@ class ChosePanel {
         if (!num) {
             num = this.data.cartInfo && this.data.cartInfo.num || 1;
             if (selectSku && selectSku.skuId !== this.cartSkuId) {
-                num = this.minBuyNum || 1;
+                num = +selectSku.storage >= +this.minBuyNum ? this.minBuyNum : 1;
             }
         }
         return num;