[FIX] web: avoid domains with empty list

After loading the calendar view, making a search with an inactive
domain in the list will trigger a search "partner_ids not in []" which
returns zero result.
The code intention was to initialise the avoidValues, not to send an
empty list.

To reproduce the issue:
1. create an event shared between user 1 and 2
2. as user 2, open the Calendar menu
-> shared event is present
3. click on "week" tab (forcing a refresh)
-> shared event no longer appears

Fixes odoo/odoo#39839

closes odoo/odoo#40264

X-original-commit: 299a6dbc
Signed-off-by: Martin Trigaux (mat) <mat@odoo.com>