Selecting Media File as image block link creates blob URL if large image still being processed

[ianmjones]

Steps to reproduce...

1. In post editor, select image block.
2. Use "Upload" button.
3. Select a large file, e.g. 5120x2880 image.
4. While the image is still being processed (has spinner overlay), select link button on the block and pick "Media File".

When the post is then saved and viewed, the wrapping link will have an href with a value like "blob:http://example.com/cee61eeb-3bf1-984a-9930-5660bba8a2f8".

If you then go back and edit the post, remove the link from the block, and then re-select Media File as the link type and save the post, expected URL used in post, e.g. "​http://example.com/wp-content/uploads/2019/10/image-scaled-2560.png"

Tested with WP 5.3-RC3.

[desrosj]

Moving into the milestone for visibility and testing.

[azaozz]

This looks like a side-effect of showing a preview of the image while it is being uploaded and post-processed. Don't think it is a new regression in 5.3.