The right of a director, officer, employee, or agent to indemnification or to advancement of expenses arising under a provision in the articles of incorporation or a bylaw shall not be eliminated or impaired by an amendment to or repeal of that provision after the occurrence of the act or omission that is the subject of the proceeding for which indemnification or advancement of expenses under that provision is sought, unless the provision in effect at the time of such an act or omission explicitly authorizes the elimination or impairment of the right after such an action or omission has occurred.