efi_loader: image_loader: retrieve authenticode only if it exists

Since the certificate table, which is indexed by
IMAGE_DIRECTORY_ENTRY_SECURITY and contains authenticode in PE image,
doesn't always exist, we should make sure that we will retrieve its pointer
only if it exists.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
1 file changed