pref(instance): 概览数据增加默认值，避免出现NaN问题

src/pages/instance/index.tsx

@@ -113,7 +113,12 @@ const Instance = () => {
     pageSize: 10
   });
   const [searchOptions, setSearchOptions] = useState([]);
-  const [overviewData, setOverviewData] = useState({});
+  const [overviewData, setOverviewData] = useState({
+    avgTime: 0,
+    runningNum: 0,
+    successNum: 0,
+    failureNum: 0
+  });
   const [searchParams, setSearchParams] = useState({
     appId: '',
     state: '',