If your home is accidentally destroyed and you then dispose of the vacant land on which it was built, you can choose to apply the main residence exemption as if the home had not been destroyed and continued to be your main residence.
You can get a full exemption for the land if you used it solely for private purposes in association with your home and it does not exceed two hectares. You cannot claim the main residence exemption for this period for any other dwelling, except for a limited time if you are changing main residences, see Moving from one main residence to another.
You can only get this exemption where your home was accidentally destroyed. If the destruction of your home is intentional and just after the destruction you sell the vacant block of land, you cannot get the main residence exemption.