Video Component or Custom HTML iframe

When using a video in Custom HTML


iframe> the size constraints of the container holding the custom html works fine in Firefox but not in Safari.

When actual video is defined and can be found at a url, the custom code works in both browsers.

When the video results in a 404 error, the sizing in Safari does not work.

Why is this a bug? If there's nothing to populate the iframe with, how can it have a size?