In case a blend file opening fails (in the context of library content
listing, e.g. for linking or appending), the File Browser would just
show an emtpy window.
With the new comnpatibility policy, this will now become a fairly common
situation, which requires giving proper explanations to the user.
This commit re-uses and extends the system used to display errors
messages from the Asset browser.
Part of #109151 (PR !110109).
aecf6dd1db