I've not had this happen, but from what I gather, the stock roll cage spreader bars are not really that integral for roll cage/windshield support. IMO they are best used for grab handle mounting. The spreader bars won't prevent the windshield from caving in, whereas an aftermarket full roll cage provides more protection. In the stock setup, it's the main hoop that provides any measure of safety.
You could probably have the spreader bars welded back up and still have the same amount of support as from the factory.