Merge [6446] from trunk. Never return nil from read_params for compat…

…ibility with plain CGI query params parser. References #7581.

git-svn-id: http://svn-commit.rubyonrails.org/rails/branches/1-2-stable@6448 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

actionpack/lib/action_controller/cgi_ext/raw_post_data_fix.rb

@@ -65,7 +65,7 @@ def read_query
           if env_qs.blank? && !(uri = env_table['REQUEST_URI']).blank?
             uri.split('?', 2)[1] || ''
           else
-            env_qs
+            env_qs || ''
           end
         end
       end