accounts synchronisation : add checks to avoid errors/partial sync

[fphg]

For some undetermined reason, our ldap georchestra/ldap:25.0.x has been corrupted. Several organizations did not have a georchestraObjectIdentifier. In this case, the geonetwork sync crashes when encountering a corrupted account. The resulting situation is very destabilizing because:

• Anonymous users see GeoNetwork correctly
• Some authenticated users see GeoNetwork correctly
• Most users have a 500 error on /geonetwork/srv/api/me
• nothing in the different GUIs allows to diagnose

Geonetwork should ignore directory entries that may cause an error during synchronization, or issue a clear warning.

Thanks to @pmauduit who solved our problem.

[fphg]

related to #273