edit

app/shop/lib/Manage.php

@@ -510,7 +510,7 @@ class Manage
             $num = 0;
         }
         $prev = Dever::db('shop/goods_stat')->prev($where);
-        if ($prev && $prev['num'] >= 0) {
+        if ($prev && $num > 0 && $prev['num'] >= 0) {
             $n = $prev['num'];
             if ($n == 0) {
                 $n = 1;