Fix clicking unread counter

When clicking the unread counter, the following exception occurs:
```
Uncaught TypeError: Cannot read properties of null (reading 'getAttribute')
```

This is due to `onClickMainMenuListItem` not working correctly for the
unread counter `span`s, which return `null` when using `querySelector`.

internal/ui/static/js/app.js

@@ -86,7 +86,8 @@ function onClickMainMenuListItem(event) {
     if (element.tagName === "A") {
         window.location.href = element.getAttribute("href");
     } else {
-        window.location.href = element.querySelector("a").getAttribute("href");
+        const linkElement = element.querySelector("a") || element.closest("a");
+        window.location.href = linkElement.getAttribute("href");
     }
 }