Add this to the file '/core/EE_Module_Request_Router.core.php' around line 74 just inside get_route($WP) method.

testfix-request-error.php

//currently there is
public function get_route($WP) {
  $this->WP = WP
  /**more original code below here**/
}

//you want modify so you see this
public function get_route( $WP ) {
  $this->WP = WP
  if ( ! EE_Registry::instance()->REQ instanceof EE_Request_Handler )
    return NULL;
	/**more original code below here**/
}

//ONLY add the two lines I indcated above.  That is, these two lines:
if ( ! EE_Registry::instance()->REQ instanceof EE_Request_Handler )
	return NULL;