When the alt-fallback module is enabled, it will always set an alt-text for an image-block when the media attachment has one and the block's alt-text is empty. But there may be cases, where the alt-text should explicitly be empty - an empty alt-text is a valid alt-text.
We probably need a setting in the images block sidebar and maybe a (server-side) filter to allow that. An additional help-text/notice could be useful as well.
Reported by @00travelgirl00