No HTTP response code found

FIX for “No HTTP response code found” (NOTE: This is for Joomla 2.5.16 ONLY!) When attempting to upgrade an old Joomla site from v2.5.16 to 2.5.27, “No HTTP response code found” appears in the Joomla Control Panel, under the RSFirewall! Control Panel Module section. And when I go to: Components > Joomla! Update all I…