Hi

I am using the odoo15 community version and in fleet rental management I am facing an issue whenever I add a rental contract with  " 0 " first payment and add recurring amount whatever it is daily, weekly, or monthly the contract is created but when I want to generate an invoice it shows me the error

odoo server error

Traceback (most recent call last):
  File "/opt/odoo15/odoo/odoo/addons/base/models/ir_http.py", line 237, in _dispatch
    result = request.dispatch()
  File "/opt/odoo15/odoo/odoo/http.py", line 688, in dispatch
    result = self._call_function(**self.params)
  File "/opt/odoo15/odoo/odoo/http.py", line 360, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/opt/odoo15/odoo/odoo/service/model.py", line 94, in wrapper
    return f(dbname, *args, **kwargs)
  File "/opt/odoo15/odoo/odoo/http.py", line 349, in checked_call
    result = self.endpoint(*a, **kw)
  File "/opt/odoo15/odoo/odoo/http.py", line 917, in __call__
    return self.method(*args, **kw)
  File "/opt/odoo15/odoo/odoo/http.py", line 536, in response_wrap
    response = f(*args, **kw)
  File "/opt/odoo15/odoo/addons/web/controllers/main.py", line 1339, in call_button
    action = self._call_kw(model, method, args, kwargs)
  File "/opt/odoo15/odoo/addons/web/controllers/main.py", line 1327, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/opt/odoo15/odoo/odoo/api.py", line 464, in call_kw
    result = _call_kw_multi(method, model, args, kwargs)
  File "/opt/odoo15/odoo/odoo/api.py", line 451, in _call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/opt/odoo15/odoo-custom-addons/fleet_rental/models/car_rental.py", line 579, in action_invoice_create
    raise Warning("Please enter advance amount to make first payment")
Exception

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/opt/odoo15/odoo/odoo/http.py", line 644, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/opt/odoo15/odoo/odoo/http.py", line 302, in _handle_exception
    raise exception.with_traceback(None) from new_cause
odoo.exceptions.Warning: Please enter advance amount to make first payment