The effect of a difference between the articles and bylaws in the statement of the number of directors shall not be governed by subdivision (a) of Section 212 of the new law for a corporation existing on the effective date, which shall continue to be governed by the prior law, unless and until an amendment of its articles is filed pursuant to Section 2302. If such amendment makes any change in the number of directors or the maximum or minimum number of directors or makes a change from a fixed to a variable board or vice versa, it shall also be approved by the outstanding shares (Section 152).