write_add_filter_bzip2: End compression in the freer

write_add_filter_bzip2: End compression in the freer

If a fatal error occurs, the closer will not be called, so neither will
BZ2_bzCompressEnd(), and we will leak memory.  Fix this by calling it a
second time from the freer.  This is harmless in the non-error case as
it will see that the compression state has already been cleared and
immediately return BZ_PARAM_ERROR, which we simply ignore.