(a) A foreign corporation transacting business in this state without a certificate of authority may not maintain a proceeding in any court in this state until it obtains a certificate of authority.

(b) The successor to a foreign corporation that transacted business in this state without a certificate of authority and the assignee of a cause of action arising out of that business may not maintain a proceeding based on that cause of action in any court in this state unless before the commencement of the proceeding the foreign corporation or its successor obtains a certificate of authority.

(c) Notwithstanding subsections (a) and (b) of this Code section, the failure of a foreign corporation to obtain a certificate of authority does not impair the validity of its corporate acts or prevent it from defending any proceeding in this state.