Fix snippest sidebar when signed out.

app/views/layouts/nav/_snippets.html.haml

 %ul.nav.nav-sidebar
-  = nav_link(path: user_snippets_path(current_user), html_options: {class: 'home'}) do
-    = link_to user_snippets_path(current_user), title: 'Your snippets', data: {placement: 'right'} do
-      = icon('dashboard fw')
-      %span
-        Your Snippets
+  - if current_user
+    = nav_link(path: user_snippets_path(current_user), html_options: {class: 'home'}) do
+      = link_to user_snippets_path(current_user), title: 'Your snippets', data: {placement: 'right'} do
+        = icon('dashboard fw')
+        %span
+          Your Snippets
   = nav_link(path: snippets_path) do
     = link_to snippets_path, title: 'Discover snippets', data: {placement: 'right'} do
       = icon('globe fw')