Fixed bad when selecting same page as parent.

app/helpers/pages_helper.rb

@@ -48,4 +48,8 @@ module PagesHelper
       end
     end
   end
+
+  def parent_pages_to_select(current_page)
+    Page.non_redirected.reject { |p| p == current_page }
+  end
 end

app/views/pages/_form.html.haml

@@ -97,6 +97,6 @@
     |
     = link_to "Abbrechen", @page
     | Oberseite ändern:
-    = collection_select(:page, :parent_id, Page.non_redirected, :id, :permalink, {:prompt => "Neue Oberseite?", :include_blank => true})
+    = collection_select(:page, :parent_id, parent_pages_to_select(@page), :id, :permalink, {:prompt => "Neue Oberseite?", :include_blank => true})
 
 %div(style="clear:right; height:1px")