The fridge should continue to work so long as you have power to the controller. If you don't have a good charge line, energy in the batteries will be the limiting factor. I've not had my fridge flame blow out at 60 mph running into 20 mph winds.
If a crash causes a rupture in the LPG lines, a flow limiting valve at the tank should shut it off.
It is a good idea to shut off the fridge, and any other pilot light or spark ignition LPG appliances, at fuel stops, not because of problems with vapors, but because in these days of self service pumping, every so often somebody sprays fuel on all the vehicles around them.
