The intestate share of the surviving spouse is determined as follows:
A. as to separate property:
(1) if there is no surviving issue of the decedent, the entire intestate estate; or
(2) if there is surviving issue of the decedent, one-fourth of the intestate estate; and
B. as to community property, the one-half of the community property as to which the decedent could have exercised the power of testamentary disposition passes to the surviving spouse.