(1)  Except as provided by subsection (2) , where a beneficial disposition is made by a will to a person who attests the execution of the will, the disposition is void so far only as concerns that person or any person claiming under that person.

(2)  A beneficial disposition made by a will is not made void by subsection (1) if –

(a) more than 2 persons have attested the execution of the will and at least 2 of them are not persons to whom any such disposition is made or the spouses of any such persons; or

(b) all the persons who would benefit directly from the avoidance of the disposition consent in writing to the distribution of the disposition according to the will and they all have capacity at law to do so.

(3)  Notwithstanding anything contained in this section, a person who attests the execution of a will is a competent witness to prove the execution of the will or its validity or invalidity.