Fix crash when no Bluetooth feature in Settings

- Move PreferenceGroup init method out of isAvailable() condition,
  then PreferenceGroup will not be null.
- Update getAvailabilityStatus(), since the controller now may have usb
  and dock.

Bug: 110712414
Test: make -j42 RunSettingsRoboTests
Change-Id: I4d85a42c26fb20d319e7321177b271933be3fdb0

src/com/android/settings/connecteddevice/AvailableMediaDeviceGroupController.java

@@ -83,9 +83,11 @@ public class AvailableMediaDeviceGroupController extends BasePreferenceControlle
     @Override
     public void displayPreference(PreferenceScreen screen) {
         super.displayPreference(screen);
+
+        mPreferenceGroup = screen.findPreference(KEY);
+        mPreferenceGroup.setVisible(false);
+
         if (isAvailable()) {
-            mPreferenceGroup = screen.findPreference(KEY);
-            mPreferenceGroup.setVisible(false);
             updateTitle();
             mBluetoothDeviceUpdater.setPrefContext(screen.getContext());
             mBluetoothDeviceUpdater.forceUpdate();