Black hole is a layer that is used internally in wildfire to store hidden items, but it is not suppose to show up in the layer tree after datecode 2003210. Did it somehow get added as an option in your config.pro file?
i noticed the black_hole layer while inserting shared data (an emptyiges logo) in the model. the import information windownotified me a black hole layer was inserted into model. that was the first time i have ever seen the black hole layer. Op sys WF2