Fix SysUI Demo Mode activity so it doesn't crash.

Test: Settings > Developer Options > System UI demo mode > verify you
see an activity and it doesn't crash

Change-Id: I883a4fbcbab8f14275a5a6ed0d8a4095a22ada05

packages/SystemUI/src/com/android/systemui/tuner/TunerActivity.java

@@ -54,6 +54,7 @@ public class TunerActivity extends Activity implements
 
     protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
+        setTheme(R.style.Theme_AppCompat_DayNight);
 
         getWindow().addFlags(WindowManager.LayoutParams.FLAG_DRAWS_SYSTEM_BAR_BACKGROUNDS);
         requestWindowFeature(Window.FEATURE_NO_TITLE);