In any
of the following circumstances, it is not necessary to perform any
act under, or perform, a contract:
(a) If either party to a contract waives the other party from
fulfilling the obligation under the contract,
(b) If a voidable contract is voided by the party entitled to
do so,
(c) If the contract cannot be performed for the reason of its
breach by the other party,
(d) If it is not necessary to perform the act under the
contract by operation of any provision of this Part,
(e) If a contract which is unenforceable according to
Section 531.