The commissioner shall revoke the authority of a domestic mutual insurer to issue policies without contingent liability if at any time the insurer’s assets are less than the sum of its liabilities and the surplus required for such authority or if the insurer, by resolution of its board of directors approved by a majority of its members, requests that the authority be revoked. During the absence of such authority, the insurer shall not issue any policy without providing therein for the contingent liability of the policyholder nor renew any policy which is renewable at the option of the insurer without endorsing the same to provide for such contingent liability.