Show emtpy state if now feature flags exist

app/views/projects/feature_flags/_list.html.haml

@@ -4,6 +4,11 @@
     .badge.badge-pill
       = @feature_flags.count
   %ul.content-list.pages-domain-list
+    - if @feature_flags.empty?
+      %li
+        .nothing-here-block
+          = s_('FeatureFlags|No feature flags found.')
+    - else
       - @feature_flags.each do |feature_flag|
         %li.pages-domain-list-item.unstyled
           = feature_flag.name