Never return nil from CGI#read_query for compatibility with plain CGI query params parser. Closes #7581.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@6446 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/cgi_ext/raw_post_data_fix.rb

@@ -68,7 +68,7 @@ class CGI #:nodoc:
           if env_qs.blank? && !(uri = env_table['REQUEST_URI']).blank?
             uri.split('?', 2)[1] || ''
           else
-            env_qs
+            env_qs || ''
           end
         end
       end