Each commission may adopt regulations with respect to disqualification of members or alternates from participating in the review of a proposal. In the absence, however, of those regulations, Section 56332 or 56335 shall apply. The representation by a member or alternate of a city or district shall not disqualify, or be cause for disqualification of, the member or alternate from acting on a proposal affecting the city or the district, and any regulation providing for the disqualification of a city or district representative for that reason is null and void.