Zero length file name isn't really valid. So check the length of the
final file name generated by udf_translate_to_linux() and return -EINVAL
instead of zero length file name. Update caller of udf_get_filename() to
not check for 0 return value.
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jan Kara <jack@suse.cz>