When generating a short url via the API your get a blank response and 500 error code returned. Actual error in the server logs:
PHP Fatal error: Call-time pass-by-reference has been removed in /home/path/public_html/api/library/Api/Parser/Xml.php on line 51
Edit /api/library/Api/Parser/Xml.php. Find:
$this->encode($this->root_element, $this->_data, &$root);
Replace with:
$this->encode($this->root_element, $this->_data, $root);