Describe the bug
The image block link option links to the thumbnail selected, not the original image.
This doesn't allow to make lightbox behaviour for example, and this was the classic editor behaviour.

To Reproduce
Steps to reproduce the behavior:

1. Go to an article
2. Insert one image
3. Select on right panel a thumbnail for the display
4. On the "Link settings" select Media file

Expected behavior
The source media url is used instead of the thumbnail.

Desktop (please complete the following information):

• OS: OSX
• Browser : chrome
• Version : last

Just changing the line

to use the source_image can fix the issue in my opinion.