修复结算校验bug. code review by ZB

@@ -133,15 +133,16 @@ if ($('.freebie').length > 0) {
 }
 
 $('.btn-balance').on('touchend', function() {
-    if (shouldSelectGift()) {
-        showChooseGifDialog();
-        return false;
-    }
     if (shouldLowStocks()) {
         tip.show('库存不足无法结算');
         return false;
     }
 
+    if (shouldSelectGift()) {
+        showChooseGifDialog();
+        return false;
+    }
+
     if (hasChecked) {
         window.location.href = '/cart/index/orderEnsure?cartType=' + cartType;
     } else {

@@ -190,6 +190,10 @@ function bottomCheckBoxHandeler(isSelected, type, handlerAfterTouch) {
 
 //全选按钮点击事件
 $selectAllBtn.on('touchend', function() {
+    if ($('.low-stocks').length > 0) {
+        tip.show('所选商品中含有库存不足的商品');
+        return false;
+    }
     bottomCheckBoxHandeler($(this).hasClass('icon-cb-checked'), $('#cartType').val(), didUpdateAllGoodsCheckStatus);
 });