Mobs Spawning From Spawners Leave "Ghost" Entity At World Spawn

I have got spawners in the world, which have a custom data tag. What I expected to happen was the mobs to spawn normally. What actually happened was although they did spawn normally, they left these "ghost" entity's at 0 0 0. If that mob had custom data, they would be included in the "ghost" entity of itself. I have tested this out on other worlds, and it seems to still be there.