fs/ntfs3: Add null pointer checks

commit fc499245 upstream.

Added null pointer checks in function ntfs_security_init.
Also added le32_to_cpu in functions ntfs_security_init and indx_read.

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Cc: "Doebel, Bjoern" <doebel@amazon.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>