Close TinyMCE plugin window on click away

You asked the question a long ago but I was looking for something similar and found a solution.

Enqueue an admin side script on post edit screens(where we have tinyMCE). Then use the code below:

(function($) {
    'use strict';

    $(document).ready(function() {
        $(document).on( 'click', '#mce-modal-block', function() {
            tinyMCE.activeEditor.windowManager.close();
        });
    });

})(jQuery);

This way you can close any popup comes from tinyMCE by clicking outside of it.