Fix null pointer exception when updating rotation tile.

This occurs when switching users on devices that
don't have a rotation lock quick settings tile.

Change-Id: I738ca15ca754be90cec7eaf3a8eda3e38ed96b33

packages/SystemUI/src/com/android/systemui/statusbar/phone/QuickSettingsModel.java

@@ -393,7 +393,7 @@ class QuickSettingsModel implements BluetoothStateChangeCallback,
                 mInversionObserver.startObserving();
                 mContrastObserver.startObserving();
                 mColorSpaceObserver.startObserving();
-                onRotationLockChanged();
+                refreshRotationLockTile();
                 onBrightnessLevelChanged();
                 onInversionChanged();
                 onContrastChanged();