[FIX] hr_holidays: show widget when no department

The `leave_stats` widget would crash if there was no department attached
to the employee/leave request.

closes odoo/odoo#100775

Signed-off-by: Kevin Baptiste <kba@odoo.com>

addons/hr_holidays/static/src/leave_stats/leave_stats.js

@@ -40,7 +40,7 @@ export class LeaveStatsComponent extends Component {
     }
 
     get department() {
-        return this.props.record.data.department_id.data;
+        return this.props.record.data.department_id && this.props.record.data.department_id.data;
     }
 
     get employee() {