If no subscribing witness is available as a witness within the meaning of Section 240 of the Evidence Code, the court may, if the will on its face conforms to all requirements of law, permit proof of the will by proof of the handwriting of the testator and one of the following:
(a)
Proof of the handwriting of any one subscribing witness.
(b)
Receipt in evidence of one of the following documents reciting facts showing due execution of the will:
(1)
A writing in the will bearing the signatures of all subscribing witnesses.
(2)
An affidavit of a person with personal knowledge of the circumstances of the execution.