Fix null dereference in SweepInterpreterCaches am: 6a05d70393 am: 731076f33b

Original change: https://android-review.googlesource.com/c/platform/art/+/2194755

Change-Id: I0fa179bbaec9105fcc469388640471ef73a23741
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>