load dbc error

[zhaoxian1989]

code

This line was originally intended to import the content of the ECU. However, because it is a query during the import process and no instance is created, the query result return None, which leads to an error.
I would suggest changing it to look like below:

ecu=db.ecu_by_name(
                        temp.group(2))
                    if not ecu:
                        ecu=canmatrix.Ecu(temp.group(2))
                        db.add_ecu(ecu)
                    ecu.add_attribute(
                        temp.group(1),
                        temp.group(3))