TINY-1644: fixed issue with fontselect throwing errors on a hidden editor on firefox
TINY-1644: fixed issue with fontselect throwing errors on a hidden editor on firefox

tinymce/tinymce,tinymce/tinymce,FernCreek/tinymce,danielpunkass/tinymce,danielpunkass/tinymce,FernCreek/tinymce,TeamupCom/tinymce,danielpunkass/tinymce,tinymce/tinymce,TeamupCom/tinymce,FernCreek/tinymce