[FIX] hr_attendance: allow multiple attendances

If the search returns more than one result, the rendering of the message would
crash (SingletonError when accessing check_in field value).

Use the same order and limit as both search before and after

Courtesy of David Tran

Closes odoo/odoo#28055

addons/hr_attendance/models/hr_attendance.py

@@ -81,7 +81,7 @@ class HrAttendance(models.Model):
                     ('employee_id', '=', attendance.employee_id.id),
                     ('check_out', '=', False),
                     ('id', '!=', attendance.id),
-                ])
+                ], order='check_in desc', limit=1)
                 if no_check_out_attendances:
                     raise exceptions.ValidationError(_("Cannot create new attendance record for %(empl_name)s, the employee hasn't checked out since %(datetime)s") % {
                         'empl_name': attendance.employee_id.name_related,