perf: fix CLS issue of actuator page (#840)

#### What type of PR is this?

/kind improvement

#### What this PR does / why we need it:

修复 Actuator 页面抖动的问题。

#### Which issue(s) this PR fixes:

Fixes https://github.com/halo-dev/halo/issues/3225

#### Special notes for your reviewer:

测试方式：

1. 测试进入系统概览页面是否会出现 https://github.com/halo-dev/halo/issues/3225 中提到的页面抖动问题。

#### Does this PR introduce a user-facing change?

```release-note
修复 Console 端进入系统概览页面会抖动的问题。
```

src/modules/system/actuator/Actuator.vue

@@ -50,7 +50,7 @@ const handleFetchActuatorStartup = async () => {
 
 const isExternalUrlValid = computed(() => {
   if (!globalInfo.value?.externalUrl) {
-    return false;
+    return true;
   }
   const url = new URL(globalInfo.value.externalUrl);
   const { host: currentHost, protocol: currentProtocol } = window.location;