"Save offline" not working after failing to edit a found log

[moving-bits]

This is a follow-up to #15665:

On receiving the error 422 "Unprocessable entity" on trying to edit a found log a dialog box appears where you can select "save offline" to locally keep the changes you wanted to publish.

This does not work, though, it still has the old text stored offline after closing the dialog, your changes are lost.