ui: add fallback for profile background image

packages/ui-default/templates/user_detail.html

@@ -5,7 +5,7 @@
 {{ set(UiContext, 'udoc', udoc) }}
 <style>
   .user-profile-bg {
-    background-image : url("{{ udoc.backgroundImage }}");
+    background-image: url("{{ udoc.backgroundImage }}"), url("/components/profile/backgrounds/1.jpg");
   }
 </style>
 <div class="row">