Updated parser to make sure both iframes and images always have an alt text (which is set to a filler text if no alt is provided by the HTML); fixed issue where images would incorrectly be seen as having a caption if the caption contained only spaces. This also fixes the PropTypes error that would be throw by iframe contentItems not having an alt prop.
Updated parser to make sure both iframes and images always have an alt text (which is set to a filler text if no alt is provided by the HTML); fixed issue where images would incorrectly be seen as having a caption if the caption contained only spaces. This also fixes the PropTypes error that would be throw by iframe contentItems not having an alt prop.

OpenWebslides/OpenWebslides,OpenWebslides/OpenWebslides,OpenWebslides/OpenWebslides,OpenWebslides/OpenWebslides