Show message if user tries to fork and has no available namespaces

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

 - page_title "Fork project"
+- if @namespaces.present?
   %h3.page-title Fork project
   %p.lead
     Click to fork the project to a user or group
@@ -31,6 +32,10 @@
       Fork is a copy of a project repository.
       %br
       Forking a repository allows you to do changes without affecting the original project.
+- else
+  %h3 No available namespaces to fork the project
+  %p.slead
+    You must have permission to create a project in a namespace before forking.
 .save-project-loader.hide
   .center