No reference info for Addon Manager causes an exit

[romjerome]

@emyoulation

I think this was a case that is highly unlikely: no addons-en.json exists and no internet connection exit that would allow it to be downloaded.

I cannot see the relation with addons.

Note, maybe this could also match the time for the metadata table creation (e.g., surname list creation at the end of the session) and the default set of gramplets (around names) on dashboard for the first gramps session ?