What if Buyer Does NOT Have Enough Funds to Close on New House

[NA NA]

I am currently purchasing a new construction home and am under contract to close on June 14. To help with the down payment and meet the lender requirements, I am selling my current home to help get around $190k. I am worried that I will not have enough time for a buyer to close on my current home, and I will be short almost $200k at closing for my new house. What can I do/happen if I do not have the money to close on my new house?