[feature/request-class] request_var should return after setting the request object.

If the "dependency injection" mechanism is used there should not be any regular
computation of a result value. request_var has to return immediately.

PHPBB3-9716

phpBB/includes/functions.php

@@ -49,6 +49,7 @@ function request_var($var_name, $default, $multibyte = false, $cookie = false)
 	if ($var_name instanceof phpbb_request_interface)
 	{
 		$request = $var_name;
+		return;
 	}
 
 	// no request class set, create a temporary one ourselves to keep backwards compatability