If a person who is chosen as a member of the State Board of Equalization is not an inhabitant of the district for which he is chosen, or if a member of that board ceases to be an inhabitant of the district for which he is chosen, a vacancy occurs in the board, but a member duly qualified at the time of his election or appointment shall not during his term of office become disqualified because of any change which the Legislature makes in the boundaries of the equalization districts.