Bug: Fleet Appearing in Undiscovered Sector

Don't know if anyone else has had this, but oh well.
Upon completion of the Tyranids Invasion part 1 (the mission where you must defend Agripinaa, Belis Corona and Nemesis Tessera from a huge invasion), it gave me three fleets for successfully defending them. However, one of the fleets spawned within the Belial Sector, a sector that I haven't discovered yet. Completely locked down, can't do anything with it. Please fix.

I had the same thing. Useless fleet chewing through my upkeep until I progressed enough in the story to open that sector. I think mine was caused because I had three fleets in the system it was supposed to spawn so it took the jump to Belial rather than spawning in an available Nemesis Tessera system.