varbase_media_twitter does not handle SVG thumbnails created by Media Entity Twitter's "Generate thumbnails" option

In the Media Library, accessed from ckeditor, embedded tweets are invisible/unselectable if they are generated when media_entity_twitter's "Generate Thumbnail" option is on. These thumbnails are SVGs. They are correctly generated. They are visible in the filesystem and if one goes to the Media Library at admin/content/media.

I'm not very familiar with the system, but judging by the HTML, this relates to varbase_media's browser_teaser object, which seems to be the wrapper for the thumbnails (both missing and visible). I am guessing this doesn't handle SVGs. It seems to handle normal images and videos and no images (e.g. the other tweets visible in the screengrabs, which were generated with the "Generate Thumbnail" option off.

A kludge is to simply leave "Generate Thumbnail" off. The tweets embed OK, but they are invisible in ckeditor. I was hoping that the thumbnail would make a placeholder visible in ckeditor.