Handle closed socket and NPE properly am: 8f4adaedaf

Original change: https://android-review.googlesource.com/c/platform/packages/modules/Connectivity/+/2745875

Change-Id: Ibb722a51010492ef45153228bfbea484c5c95f7f
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>