I have seen some answers on this similar question they all point to same thing that pressure outside is zero so from $W = p.\Delta V$, work done will be zero or as said in the answer from @ssavec that there is no force acting on the piston, the point is that you cannot have a balloon in space, it will burst due to inner pressure.
My physics teacher gave another perspective for this situation which in my opinion is much more relevant. It goes like this:
Since the gas is in a vessel with massless piston, then it will definitely have some pressure in normal conditions and even in vacuum, but the twist here is that, this pressure once pushes the piston and after that because piston had no resistance, it went out with some constant velocity. There was no direct force and displacement relation but just a sudden push from gas which made piston leave immediately.