title: Why do I get a 404 error and what does no Firebase App '[DEFAULT]' mean?
body: <p>What does it exactly mean and how do I solve it?</p>
  
  <pre class="lang-none prettyprint-override"><code>Failed to load resource: the server responded with a status of 404 ()
  firebaseNamespaceCore.ts:106 Uncaught FirebaseError: Firebase: No Firebase App '[DEFAULT]' has been created - call Firebase
  App.initializeApp() (app/no-app).
       at f (https://www.gstatic.com/firebasejs/7.9.1/firebase.js:1:73499)
       at Object.i [as auth] (https://www.gstatic.com/firebasejs/7.9.1/firebase.js:1:73757)
       at https://superx-bcf15.web.app/:37:22
  </code></pre>