If we fail to get bitmap info, we must not leak the encryption info.

Fixes: b8968c87
Fixes: Coverity CID 1421894
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20200320183620.1112123-1-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Tested-by: Andrey Shinkevich <andrey.shinkevich@virtuozzo.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>