Traceback (most recent call last):
  File "/opt/odoo/odoo10/odoo/http.py", line 640, in _handle_exception
    return super(JsonRequest, self)._handle_exception(exception)
  File "/opt/odoo/odoo10/odoo/http.py", line 677, in dispatch
    result = self._call_function(**self.params)
  File "/opt/odoo/odoo10/odoo/http.py", line 333, in _call_function
    return checked_call(self.db, *args, **kwargs)
  File "/opt/odoo/odoo10/odoo/service/model.py", line 101, in wrapper
    return f(dbname, *args, **kwargs)
  File "/opt/odoo/odoo10/odoo/http.py", line 326, in checked_call
    result = self.endpoint(*a, **kw)
  File "/opt/odoo/odoo10/odoo/http.py", line 935, in __call__
    return self.method(*args, **kw)
  File "/opt/odoo/odoo10/odoo/http.py", line 506, in response_wrap
    response = f(*args, **kw)
  File "/opt/odoo/odoo10/addons/web/controllers/main.py", line 889, in call_button
    action = self._call_kw(model, method, args, {})
  File "/opt/odoo/odoo10/addons/web/controllers/main.py", line 877, in _call_kw
    return call_kw(request.env[model], method, args, kwargs)
  File "/opt/odoo/odoo10/odoo/api.py", line 681, in call_kw
    return call_kw_multi(method, model, args, kwargs)
  File "/opt/odoo/odoo10/odoo/api.py", line 672, in call_kw_multi
    result = method(recs, *args, **kwargs)
  File "/opt/odoo/odoo10/addons/account/models/account_invoice.py", line 579, in action_invoice_open
    to_open_invoices.action_move_create()
  File "/opt/odoo/custom_addons/round_off_invoices/models/config.py", line 193, in action_move_create
    'amount_currency': diff_currency and amount_currency,
UnboundLocalError: local variable 'amount_currency' referenced before assignment