[FIX] web: grouped Kanban: traceback on click during reload

Have a grouped Kanban view with an x2many field. Interact with the
searchview, and then click anywhere.

The fetch of the x2many relational data is batched for the whole view
a single RPC for all groups) since e10fd346.

If the click occurs before all search_read are done (i.e. before the
fetch of relational data is started), there is a crash.

This is due to a call to get({raw: true}) to obtain the current model's
state, which is currently being reloaded and in an intermediate state.
Ideally, this shouldn't happen, but with the sync API of get, we can't
change that easily. So at most, we can ensure that it doesn't crash.
Moreover, sensitive functions requesting the state for the data can do
that in the mutex to ensure that the state isn't currently being reloaded.

Related to Issue: 1937149

closes odoo/odoo#32587

Signed-off-by: Géry Debongnie (ged) <ged@openerp.com>


Co-authored-by: Mohammed Shekha <msh@openerp.com>
Co-authored-by: Aaron Bohy <aab@odoo.com>