I'm going to side with Claret on this one, even if the fuel had ignited the forward speed of the aircraft and the pressure of the fuel being dumped would prevent the flames from climbing back up to the wing tip, and even if they did all the crew would need to do is turn the dump off and out goes the flame.
Also
Ohh and by the way, a match doesnt even nearly resemble the temperatures from a turbine section!!
As the fuel is not being sent into the inner sections of the turbine, and even if it was that engine was no longer running, I don't perceive their to be any ignition risk from the turbine.