fix: 404 page not working

Author: Miodec

frontend/src/404.html

@@ -12,6 +12,7 @@
     </script>
     <load src="html/warnings.html" />
     <div id="app" class="content-grid focus">
+      <div id="backgroundLoader" class="hidden"></div>
       <header class="focus">
         <a id="logo" href="/" router-link="">
           <div class="icon">