In this case (the non-async close case), we don't ever delete the allocated `BGCloseInfo` because [line 1209](https://github.com/basho/leveldb/blob/1b3b6ab35eb794e51eefee131c2ac04542c489fd/util/env_posix.cc#L1209) was changed to assume that `BGCloseInfo` was submitted to/deallocated by the thread pool -- which isn't true in this case. I think we just need a `delete ptr` after the `BGFileUnmapper2(ptr)` call here.