In the portal view of tasks, we set a default groupby in _prepare_task_values to project. However, since this method is called every time we change the groupby, it is effectively impossible to group by anything other than project. This commit fixes this so that it is possible to select other groupbys. Task-3438490 closes odoo/odoo#134378 X-original-commit: 02629788f24efb4646703cf94f1a8c603179e185 Related: odoo/enterprise#46945 Signed-off-by: Xavier Bol (xbo) <xbo@odoo.com>