Fix compute week

Author: Adrià Pallejà

shift_attendance/models/attendance_sheet.py

@@ -273,6 +273,8 @@ def _compute_week(self):
             for shift in rec.expected_shift_ids:
                 if shift.task_id.planning_id.name:
                     rec.week = shift.task_id.planning_id.name
+                else:
+                    rec.week = 1
 
     @api.depends("notes")
     def _compute_is_annotated(self):