Check size of grantors before indexing into the vec am: 2b686fcd97 am: ca82973033 am: 75b22bfaa5 am: 683af4f033

Original change: https://android-review.googlesource.com/c/platform/system/libhidl/+/2113745

Change-Id: I1debda2a7121f7a6f92f53a31d8631b841764328
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>