Make metered wifi controller resilient to null config

Apparently the wifi config can sometimes come back as null
initially when the device auto-connects to a network. This CL simply
makes the controller resilient to that so that it doesn't crash the
app.

Test: robotests
Bug: 73076869
Change-Id: I99098f35df9cd902f5f244a872cce9b71c17c224
2 files changed