Sometimes after a series of unfortunate events the Buyer, or more likely the Seller of a parcel land dies after signing a binding contract for the purchase, but prior to completion (and signing the transfer).
At common law, where a contract was for “personal services”, the death of the party providing those services would “frustrate” the contract making it impossible to perform. For example, a man’s promise to marry was not held to be binding after his death (Mc Bride  SCR 202).
This is not the situation for Real Estate Contracts. Real Estate Contracts are financial obligations and the foundation or subject matter of the contract, being real property, continues to exist after the death of any one of the parties. Canadian courts have consistently upheld the principal in Witicki v. Midley  6 WWR 471, wherein a contract for the sale of land was binding on the deceased’s estate despite the seller dying prior to signing the transfer document.
But… procedurally, the executor cannot sign the transfer until probate is granted… what happens? Usually, the parties (and their lawyers) will grant a pre-closing possession/ tenancy on the strength of having all the necessary documents (except the transfer) held in trust until such a time as probate can be granted.