* [CHD-3395] [Worklists/Custom Fields/Subtotals] Fixed an issue where worker-based custom fields could display two '(nobody)' subtotals depending on if the fields were NULL or zero.
* [CHD-3393] [Virtual Attendants/Worker/Availability] When setting a worker variable from a Virtual Attendant action, workers may be now be filtered by their calendar availability.
* [CHD-3389] [Mail/Worklists/Usability] Ticket worklists can now display and export the given name (first) and surname (last) of the 'first wrote' and 'last wrote' sender email addresses.
6.4.2-release checkpoint
Merge branch '6.4.2' into stable