Media image link url not updated with save all changes in multisite

[ev3rywh3re]

In the attachments modal window you can normally change and set the Link URL and save it pressing Save all changes. This behavior seems to be broken in sub-domain and sub-directory based multisite WordPress configurations.

On my normal WordPress trunk installs I can change the Link URL for any attachment in the media modal window no prob., but on the multisite configured WordPress trunk sites the Link URL seems to always be the /files/ URL.

So far this occurs on a couple of sites across different hosting environments.

[dd32]

see #13429