Click to activate only working in half the window

Question

I'm trying out Trumbowyg, and while it's working very well, there's an issue when it comes to clicking inside it to 'activate' it (i.e. show the cursor) to be able to start typing.

It only activates if I click in the top 40% of the window. If I click on the lower part, it doesn't activate. A screenshot makes it easier to explain, I've added two colored boxes on the screenshot; if I click in the green area, the cursors appears and I can start typing. If I click in the red area, nothing happens:

When nothing happens, it can lead to a user thinking it doesn't work.

Is there any way to fix this, so that I can click anywhere in the window to activate it?

The code I've used is very straightforward:

<form>
 <textarea name="comment" id="comment"></textarea>
</form>
<script src="https://code.jquery.com/jquery-1.9.0.js"></script>
<script src="trumbowyg/trumbowyg.min.js"></script>
<link rel="stylesheet" href="trumbowyg/ui/trumbowyg.min.css">
<script>
$('#comment').trumbowyg();
</script>

Please help!

Thank you.