When there are no files for __io_sqe_files_scm() to process in the
range, it'll free everything and return. However, it forgets to put uid.

Fixes: 08a45173 ("io_uring: allow sparse fixed file sets")
Signed-off-by: NPavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/accee442376f33ce8aaebb099d04967533efde92.1648226048.git.asml.silence@gmail.comSigned-off-by: NJens Axboe <axboe@kernel.dk>