TB 78 - address book shows a comma after entries with only last name

[BillH99999]

Your environment

TbSync version: 2.16 Thunderbird version: 78.3.1 64-bit

[ ] Yes, I have installed the latest available beta version from https://tbsync.jobisoft.de and my issue is not yet fixed, I can still reproduce it.

Expected behavior

In TB 68, entries in the address book with only a last name do not show the comma after the last name.

Actual behavior

In TB 78, entries in the address book with only a last name show a comma after the last name.

Steps to reproduce

Create a contact with only a last name and then look at it in the address book in TB 78.

TB68:

TB78:

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