Assignee choice invalidates tag/status/priority order

[altafarus-arch]

Brief description:
Tickets listed on ticket board cannot be ordered by tags, status, priority or reason value when an assignee is already chosen.

Reproducible: always

Steps to repro:

• Connect to /admin/tickets
• Select an assignee with textbox
• Click Apply
• Click on Tags (or Status/ Priority/ Reason)

Expected behavior:
Ticket list ordered by Tags (or Status/ Priority/ Reason).

Observed behavior:

• Page is reloaded
• Image of an arrowhead pointing at the bottom of the page is displayed on the right of the Tags column title to inform user tickets list is supposed to be ordered by Tags value.
• URL contains “order=tags” parameter
• Order of the tickets in the list hasn’t changed

Environment:

1. TOR Browser 9.5a11 (based on Mozilla Firefox 68.7.0esr) (32-bit)

2. Firefox Quantum 68.6.0esr (32 bits)
   with OS: 4.19.0-8-686-pae Add table #1 SMP Debian 4.19.98-1 (2020-01-26) i686 GNU/Linux

3. TOR Browser 9.0.9 (based on Mozilla Firefox 68.7.0esr) (64-bit)
   with macOS Catalina version 10.15.3
   and also with Windows 10 Professional