ethernet: add null check before reporting server interface state am: df50b6caac

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2667458

Change-Id: I79b0c386cd6e634528b5582467fdfd15724ef43a
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>