In tests, content_type can be nil, which would disturb accepts/format

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@6155 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/request.rb

@@ -78,7 +78,7 @@ def content_type
     def accepts
       @accepts ||=
         if @env['HTTP_ACCEPT'].to_s.strip.empty?
-          [ content_type, Mime::ALL ]
+          [ content_type, Mime::ALL ].compact # make sure content_type being nil is not included
         else
           Mime::Type.parse(@env['HTTP_ACCEPT'])
         end