Add a null pointer check for wifi_chip in am: 4e6349240e

Original change: https://android-review.googlesource.com/c/platform/hardware/interfaces/+/2279026

Change-Id: Ia67f4b0cca7ea6f5f55ce3857fd2c9df3169d4dd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>