fix: 过滤NaN/nan/null/空值防MySQL报错

wwwroot/discount_setting/save_discount.dspy

@@ -13,6 +13,17 @@ try:
     if not discountid or not productid:
         raise Exception('缺少必要参数: discountid, productid')
 
+    # 过滤 NaN 和空值
+    if discount_val is not None:
+        s = str(discount_val).strip().lower()
+        if s in ('', 'nan', 'none', 'null'):
+            discount_val = None
+
+    if old_discount is not None:
+        s = str(old_discount).strip().lower()
+        if s in ('', 'nan', 'none', 'null'):
+            old_discount = None
+
     # 对比新旧值，相同则跳过
     if discount_val is not None and old_discount is not None:
         try: