xmlrpclib.Fault: <Fault 255: 'unsupported operand type(s) for *: \'Decimal\' and \'float\'\nTraceback (most recent call last):\n  File "/trytond/protocols/xmlrpc.py", line 127, in _dispatch\n    session, object_type, object_name, method, *params)\n  File "/trytond/protocols/dispatcher.py", line 156, in dispatch\n    res = getattr(obj, method)(*args_without_context, **kargs)\n  File "/trytond/modules/sale/sale.py", line 1287, in on_change_with_amount\n    (vals.get(\'unit_price\') or Decimal(\'0.0\'))\nTypeError: unsupported operand type(s) for *: \'Decimal\' and \'float\'\n'>