2nd attempt handle BT is not supported on emulator

am: 59287d40d1

Change-Id: I843fc58484df106af09cae87dcb886ea49aa53ea

src/com/android/settings/sound/AudioSwitchPreferenceController.java

@@ -170,12 +170,20 @@ public abstract class AudioSwitchPreferenceController extends BasePreferenceCont
 
     @Override
     public void onStart() {
+        if (mLocalBluetoothManager == null) {
+            Log.e(TAG, "Bluetooth is not supported on this device");
+            return;
+        }
         mLocalBluetoothManager.setForegroundActivity(mContext);
         register();
     }
 
     @Override
     public void onStop() {
+        if (mLocalBluetoothManager == null) {
+            Log.e(TAG, "Bluetooth is not supported on this device");
+            return;
+        }
         mLocalBluetoothManager.setForegroundActivity(null);
         unregister();
     }

tests/robotests/src/com/android/settings/sound/AudioOutputSwitchPreferenceControllerTest.java

@@ -186,6 +186,8 @@ public class AudioOutputSwitchPreferenceControllerTest {
 
         AudioSwitchPreferenceController controller = new AudioSwitchPreferenceControllerTestable(
                 mContext, TEST_KEY);
+        controller.onStart();
+        controller.onStop();
 
         assertThat(mLocalBluetoothManager).isNull();
     }