Don't show fork button if user can't fork the project.

app/views/projects/forks/index.html.haml

@@ -29,6 +29,7 @@
           = link_to page_filter_path(sort: sort_value_oldest_updated, without: excluded_filters) do
             = sort_title_oldest_updated
 
+    - if current_user && can?(current_user, :fork_project, @project)
       - if current_user.already_forked?(@project) && current_user.manageable_namespaces.size < 2
         = link_to namespace_project_path(current_user, current_user.fork_of(@project)), title: 'Go to your fork', class: 'btn btn-new' do
           = icon('code-fork fw')