avb: Fix AvbSlotVerifyData->cmdline might be NULL

When AVB_VBMETA_IMAGE_FLAGS_VERIFICATION_DISABLED is set,
AvbSlotVerifyData->cmdline should be a NUL-terminated string
instead of NULL.

Bug: 119551429
Test: atest libavb_host_unittest

Git-repo: https://source.codeaurora.org/quic/la/platform/external/avb
Git-Commit: 9ba3b6613b4e5130fa01a11d984c6b5f0eb3af05

Change-Id: I07d8db24ace8bdd9bdeadf46803a2be36d2436a8
1 file changed