[16.0][FIX] avoid error in aged partner balance report

[huguesdk]

avoid error in aged partner balance report when processing journal items without a due date (account.move.line.date_maturity field is not set).

here is the error that happens without this fix:

Traceback (most recent call last):
  File "/home/odoo16/src/odoo/odoo/http.py", line 1638, in _serve_db
    return service_model.retrying(self._serve_ir_http, self.env)
  File "/home/odoo16/src/odoo/odoo/service/model.py", line 133, in retrying
    result = func()
  File "/home/odoo16/src/odoo/odoo/http.py", line 1665, in _serve_ir_http
    response = self.dispatcher.dispatch(rule.endpoint, args)
  File "/home/odoo16/src/odoo/odoo/http.py", line 1779, in dispatch
    return self.request.registry['ir.http']._dispatch(endpoint)
  File "/home/odoo16/src/odoo/addons/website/models/ir_http.py", line 237, in _dispatch
    response = super()._dispatch(endpoint)
  File "/home/odoo16/src/odoo/odoo/addons/base/models/ir_http.py", line 154, in _dispatch
    result = endpoint(**request.params)
  File "/home/odoo16/src/odoo/odoo/http.py", line 700, in route_wrapper
    result = endpoint(self, *args, **params_ok)
  File "/home/odoo16/src/oca/reporting-engine/report_xml/controllers/report.py", line 24, in report_routes
    return super().report_routes(
  File "/home/odoo16/src/odoo/odoo/http.py", line 700, in route_wrapper
    result = endpoint(self, *args, **params_ok)
  File "/home/odoo16/src/oca/reporting-engine/report_xlsx_helper/controllers/main.py", line 52, in report_routes
    return super().report_routes(reportname, docids, converter, **data)
  File "/home/odoo16/src/odoo/odoo/http.py", line 700, in route_wrapper
    result = endpoint(self, *args, **params_ok)
  File "/home/odoo16/src/oca/reporting-engine/report_xlsx/controllers/main.py", line 49, in report_routes
    return super().report_routes(reportname, docids, converter, **data)
  File "/home/odoo16/src/odoo/odoo/http.py", line 700, in route_wrapper
    result = endpoint(self, *args, **params_ok)
  File "/home/odoo16/src/odoo/addons/web/controllers/report.py", line 39, in report_routes
    html = report.with_context(context)._render_qweb_html(reportname, docids, data=data)[0]
  File "/home/odoo16/src/oca/account-financial-reporting/account_financial_report/models/ir_actions_report.py", line 19, in _render_qweb_html
    return super(IrActionsReport, obj)._render_qweb_html(
  File "/home/odoo16/src/odoo/odoo/addons/base/models/ir_actions_report.py", line 913, in _render_qweb_html
    data = self._get_rendering_context(report, docids, data)
  File "/home/odoo16/src/odoo/odoo/addons/base/models/ir_actions_report.py", line 928, in _get_rendering_context
    data.update(report_model._get_report_values(docids, data=data))
  File "/home/odoo16/src/oca/account-financial-reporting/account_financial_report/report/aged_partner_balance.py", line 419, in _get_report_values
    )._get_move_lines_data(
  File "/home/odoo16/src/oca/account-financial-reporting/account_financial_report/report/aged_partner_balance.py", line 240, in _get_move_lines_data
    ag_pb_data = self._calculate_amounts(
  File "/home/odoo16/src/oca/account-financial-reporting/account_financial_report/report/aged_partner_balance.py", line 74, in _calculate_amounts
    days_difference = abs((today - due_date).days)
TypeError: unsupported operand type(s) for -: 'datetime.date' and 'bool'

this error did not happen before #1140 was merged.