Clear unnecessary code (#38900)

This always seems to execute.
unless there is a special reason, I think it can declare and assign at the same time, how about this?

## Bug

- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `pnpm lint`
- [ ] The examples guidelines are followed from [our contributing doc](https://github.com/vercel/next.js/blob/canary/contributing.md#adding-examples)

packages/next/shared/lib/router/router.ts

@@ -1604,18 +1604,10 @@ export default class Router implements BaseRouter {
     }
 
     try {
-      let Component: ComponentType
-      let styleSheets: StyleSheetTuple[]
       let props: Record<string, any> | undefined
-
-      if (
-        typeof Component! === 'undefined' ||
-        typeof styleSheets! === 'undefined'
-      ) {
-        ;({ page: Component, styleSheets } = await this.fetchComponent(
-          '/_error'
-        ))
-      }
+      const { page: Component, styleSheets } = await this.fetchComponent(
+        '/_error'
+      )
 
       const routeInfo: CompletePrivateRouteInfo = {
         props,