4.—Where a party to an agreement to marry makes a gift of property (including an engagement ring) to the other party, it shall be presumed, in the absence of evidence to the contrary, that the gift—

(a) was given subject to the condition that it should be returned at the request of the donor or his personal representative if the marriage does not take place for any reason other than the death of the donor, or

(b) was given unconditionally, if the marriage does not take place on account of the death of the donor.