m4b-tool: PHP Error when splitting by chapter

When splitting by chapter I get the following error. It might well be an issue with the version of PHP installed, I really wouldn’t know.

The error has a lot of backticks so it’s messing up the markdown and I can’t figure out how to properly escape them all. You should get the idea though.

PHP Fatal error: Unparenthesized `a ? b : c ? d : e` is not supported. Use either `(a ? b : c) ? d : e` or `a ? b : (c ? d : e)` in phar:///usr/local/Cellar/m4b-tool/0.4.2/bin/m4b-tool/vendor/twig/twig/src/Node/Node.php on line 43

Fatal error: Unparenthesized `a ? b : c ? d : e` is not supported. Use either `(a ? b : c) ? d : e` or `a ? b : (c ? d : e)` in phar:///usr/local/Cellar/m4b-tool/0.4.2/bin/m4b-tool/vendor/twig/twig/src/Node/Node.php on line 43 an error occured, that has not been caught: Array ( [type] => 64 [message] => Unparenthesized `a ? b : c ? d : e` is not supported. Use either `(a ? b : c) ? d : e` or `a ? b : (c ? d : e)` [file] => phar:///usr/local/Cellar/m4b-tool/0.4.2/bin/m4b-tool/vendor/twig/twig/src/Node/Node.php [line] => 43