TYPO3.Fluid

from line 241 of the AbstractViewHelper:

1 try {
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:

 1 try {
 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 }