fix: 看板流量图实例为空判断

src/views/dashboard/overview/components/UPFFlow/index.vue

@@ -233,6 +233,7 @@ function fnGetInitData() {
 watch(
   () => upfFlowData.value,
   v => {
+    if (upfFlowChart.value == null) return;
     upfFlowChart.value.setOption({
       xAxis: {
         data: v.lineXTime,