(1) A contract to sell or let any immovable property cannot be specifically enforced in favour of a vendor or lessor-
(a) who, knowing himself not to have any title to the property, has contracted to sell or let the property;
(b) who, though he entered into the contract believing that he had a good title to the property, cannot at the time fixed by the parties or by the court for the completion of the sale or letting, give the purchaser or lessee a title free from reasonable doubt.