TYPO3.Fluid

from line 241 of the AbstractViewHelper:

1try {
2    return call_user_func_array(array($this, 'render'), $renderMethodParameters);
3} catch (\TYPO3\Fluid\Core\ViewHelper\Exception $exception) {
4    // @todo [BW] rethrow exception, log, ignore.. depending on the current context
5    return $exception->getMessage();
6}

As the todo comment states, this should be caught in production context and logged to prevent information disclosure.
Code could look something like:

 1try {
 2    return call_user_func_array(array($this, 'render'), $renderMethodParameters);
 3} catch (\TYPO3\Fluid\Core\ViewHelper\Exception $exception) {
 4    if ($this->objectManager->getContext() === 'Development') {
 5        return $exception->getMessage();
 6    } else {
 7        $this->systemLogger->log([...]);
 8        return '';
 9    }
10}