erofs-utils: complete missing memory handling

Memory allocation failure should be handled
properly in principle.

Link: https://lore.kernel.org/r/20191114091914.6789-1-hsiangkao@aol.com
Signed-off-by: Li Guifu <bluce.liguifu@huawei.com>
[ Gao Xiang: due to Huawei outgoing email limitation,
  I have to help Guifu send out his patches at work. ]
Signed-off-by: Li Guifu <blucerlee@gmail.com>
Signed-off-by: Gao Xiang <hsiangkao@aol.com>
1 file changed