I am afraid what you read was wrong. The presumption is that a party that reneges on the contract is liable for the full damages of what the contract would have paid out to the other party.
The way to offset this is if the vendor files breach of contract suit, she may have an affirmative defense of failure to mitigate. Plaintiffs have a duty to mitigate damages, meaning, they have to reasonably try to RE-RENT the space to fill the void left by her breach. If they do not try this, then the Court at discretion may take off some money, but not all.
If they DO re-rent the space for that time, then the vendor cannot get money - they cannot "double dip." Meaning, they can only get money for any time that the location stood empty because of her breach.
This is assuming that no specific verbiage in the contract augments the above common law doctrines.
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