If I understand tis thought pattern, the suggestion is that a rocket wouldn't work I the void because the usual way a rocket is described is that is generates thrust against gravity to push the rocket around. If one only uses that type of model, than one would assume that without gravity, there would be nothing to push against for the thrust to work.
That is not how a rocket actually works. Nor does the void mean the laws of physics aren't working as normal. The laws of physics are working fine. That most of the matter formed into galaxies in such a way that left a giant opening with nothing there is not out of the question. There are lots of voids where there are no galaxies. There are nine such voids within 200 million light years of Earth.