(a) Any individual generally competent to be a witness may act as a witness to a will.

(b) A will or any provision thereof is not invalid because the will is signed by an interested witness. Unless there is at least one disinterested witness to a will, an interested witness to a will is entitled to receive any property thereunder only to an amount or extent not exceeding that which is or would be the intestate share of such interested witness if the testator died intestate at the date of death.