"Maximum statement or expression depth exceeded" when using some 3rd party JavaScript libraries

Starting with Qt 5.12.1, the JavaScript engine seems to be more restrictive, which makes using some existing 3rd party JavaScript libraries impossible. I've created a stripped down example to demonstrate this here: https://gist.github.com/mhoeher/1a7a5131031f40909283936107471cb9

Basically, what I try to do is to use the 3rd party JavaScript library showdown.js to convert Markdown formatted text to HTML to display it within a QML application.

For this, I have a wrapper JavaScript library which looks like this:

Qt.include("showdown.js", function(status) {
    if (status.exception !== undefined) {
        console.warn("Failed to load showdown.js: ",
                     status.exception);
    }
});

function md2html(markdown) {
    var converter = new showdown.Converter();
    converter.setFlavor('github');
    return converter.makeHtml(markdown);
}

This worked fine up to Qt 5.12.0. However, starting with Qt 5.12.1, the library cannot be loaded anymore and on the console I get the following error message:

qml: Failed to load showdown.js:  SyntaxError: Maximum statement or expression depth exceeded

I am not sure if this new behaviour is intended, however, it makes using (some) 3rd party JavaScript libraries impossible