bug(turba): DAV sync error with two email addresses

[ralflang]

I have enabled home and work email in Turbo backends.local.php, by removing the comments for
'homeEmail' => 'object_homeemail',
'workEmail' => 'object_workemail',

It displays correct and synchronises correct if I use only one email address in the email field or use
email addresses in all 3 email fields (email, homeemail and workemail), but if I use an email address in the homeemail or
workemail field, the synchronization will fill all fields, when I make a change on the client and sometimes it will place
two email adresses in one field. I can’t see a pattern in this behaviour.

[TDannhauer]

I experience two may be related topics:

1. some contact do have a '' as email adresses ( maybe some handling of empty is not correct)
2. i have multiple contacts with (originally) one email adresse, which suddenly have a seconed email adress, which is the first one, suffixed by ',,'

[TDannhauer]

see also #45 - maybe it fixes it?

[ralflang]

Another user report on a more recent version:

I am have Horde6 RC5 with php8.4 installed and enabled in turbo’s backend.local.php homeEmail and workEmail for Contacts which have multiple Emails. When I have contacts which have 3 emails one in each field (email, home and work) it is synching correctly with the CardDav client, but if I have only one or two email addresses it fills all 3 fields and sometimes two addresses in one field. Are there any additional settings besides in backends.php which have to be changed, or has the CardDav sync app to be patched to correct this problem.
Further I noticed if you have a home address only it to synchronises the home street address to the work street address field in addition to the home street address field.