WifiP2pSettings requests network info from WifiP2pManager whenever it
gets onDeviceInfoAvailable, but sChannel may be null causing an
IllegalArgumentException. Check that sChannel is not null before
requesting network info.
Bug: 289004627
Test: atest WifiP2pSettingsTest
Change-Id: Ied8c3f8a894683d7b8e368e5c52343adb7d05e4b