Fix crash when remove network

When removing network, the update scan trigger before the disconnect.
Makes that total number of network may be one, but current network is
missing. In this situation, just return false on single network scan
check.

Bug: 151758677
Test: atest com.android.server.wifi
Change-Id: Ied0328a7db61a4aa554d0c771cb542af076a53f6
2 files changed