How to ensure seller retains the right to sue for damages ?

[Suzan Campbell]

If a buyer choose to violate a sale contract after escrow is deposited and days before closing.

No Mortgage contingency clause, No inspection contingency clause

New buyer found at a lower price.  what must the seller do to sell the property to another buyer while still retaining the ability to sue the first buyer for damages, and the difference in sale price if necessary?