A clause in any policy of life insurance policy or annuity contract providing that such policy or contract shall be incontestable after a specified period shall preclude only a contest of the validity of the policy or contract, and shall not preclude the assertion at any time of defenses based upon provisions in the policy or contract which exclude or restrict coverage, whether or not such restrictions or exclusions are excepted in such clause.   [PL 1969, c. 132, §1 (NEW).]