[Wi-Fi] Fix exception when 'Add device' with a Wi-Fi suggestion network

WifiEntry#getWifiConfiguration() may return null when
WifiEntry#isSaved() is true. Use WifiEntry#canEasyConnect()
which checks if WifiEntry#getWifiConfiguration() returns
a non-null value.

Bug: 153029289
Test: manual
      Connect to a WPA2 Wi-Fi network, click 'Add device'
      in Wi-Fi detail page and see if it crashes.
Change-Id: Ia15503eea795fdd54826699828f02c9ff95dcefa

src/com/android/settings/wifi/details2/AddDevicePreferenceController2.java

@@ -51,8 +51,7 @@ public class AddDevicePreferenceController2 extends BasePreferenceController {
 
     @Override
     public int getAvailabilityStatus() {
-        return WifiDppUtils.isSupportConfiguratorQrCodeScanner(mContext, mWifiEntry) ? AVAILABLE
-                : CONDITIONALLY_UNAVAILABLE;
+        return mWifiEntry.canEasyConnect() ? AVAILABLE : CONDITIONALLY_UNAVAILABLE;
     }
 
     @Override