Handle closed socket and NPE properly am: 8f4adaedaf am: 4596ba4bd1

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

Change-Id: I86967659e81066855330f3e0a9013d6f23db2d10
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>