fix: 修复 dataSource 不存在报错的问题

src/components/PolymericTable/NormalTable.tsx

@@ -2,7 +2,7 @@
  * @Author: XieZhiXiong
  * @Date: 2020-08-20 16:15:59
  * @LastEditors: XieZhiXiong
- * @LastEditTime: 2021-07-28 17:39:18
+ * @LastEditTime: 2021-07-29 14:08:56
  * @Description: 可以带查询的表格，内置 formily，如果需要其他Form可以传入 customRenderSearchForm 配合 reload() 实现查询
  */
 import React, { useState, useEffect, useRef, useImperativeHandle } from 'react';
@@ -90,7 +90,7 @@ const NormalTable: React.ForwardRefRenderFunction<NormalTableRefHandleType, Norm
         return {
           ...prevState,
           data: props.dataSource as T[],
-          totalCount: props.dataSource.length,
+          totalCount: props.dataSource?.length || 0,
         }
       });
     }