Exception.—This section does not extend to any person whose marriage, with such husband or wife, has been declared void by a court of competent jurisdiction, nor to any person who contracts a marriage during the life of a former husband or wife, if such husband or wife, at the time of the subsequent marriage, has been continually absent from such person for the space of 7 years, and has not been heard of by such person as being alive within that time, provided the person contracting such subsequent marriage, before the marriage takes place, informs the person with whom the marriage is contracted, of the real state of facts so far as the same are within his or her knowledge.