Civil Code, Art. 1545

Where the obligation of either party to a contract of sale is subject to any condition which is not performed, such party may refuse to proceed with the contract or he may waive performance of the condition. If the other party has promised that the condition should happen or be performed, such first mentioned party may also treat the nonperformance of the condition as a breach of warranty. Where the ownership in the thing has not passed, the buyer may treat the fulfillment by the seller of his obligation to deliver the same as described and as warranted expressly or by implication in the contract of sale as a condition of the obligation of the buyer to perform his promise to accept and pay for the thing. (n)