Handle nil type for default_homepage

src/invidious/views/template.ecr

@@ -28,7 +28,7 @@
         <div class="pure-u-1 pure-u-md-2-24"></div>
         <div class="pure-u-1 pure-u-md-20-24">
             <div class="pure-g navbar h-box">
-                <% if !env.get("preferences").as(Preferences).default_home.empty? || env.request.path != "/" %>
+                <% if !env.get("preferences").as(Preferences).default_home.to_s.empty? || env.request.path != "/" %>
                     <div class="pure-u-1 pure-u-md-4-24">
                         <a href="/" class="index-link pure-menu-heading">Invidious</a>
                     </div>