File "/home/odoo/src/enterprise/mrp_account_enterprise/reports/mrp_cost_structure.py", line 31, in get_lines total_cost_operations = self._compute_mo_operation_cost(currency_table, Workorders, total_cost_by_mo, operation_cost_by_mo, total_cost_operations, operations) File "/home/odoo/src/enterprise/mrp_workorder_hr_account/report/mrp_cost_structure.py", line 74, in _compute_mo_operation_cost total_cost_by_mo[mo_id] += cost + employee_total_cost TypeError: unsupported operand type(s) for +: 'float' and 'NoneType'