Was the starless space in "Void" the same pocket of space from "Night"?
No, the Void Void was a spatial anomaly that pulled ships in and wouldn't let them leave (almost similar to a black hole), and the Night Void was simply a vast region of space that contained no star systems and high radiation preventing light from external star systems from penetrating. Other than the radiation, there wasn't anything odd about the Night Void.
EDIT: I just remembered a third episode about a "void", the episode One
. Seven of Nine is the only crewmember capable of surviving the intense radiation in a vast nebula, so everyone else has to go into stasis chambers while they traverse the nebula.