Fix SecondaryHome exception running CarServiceTest in gcar_hl_md_emu_x86

Bug: 157234568
Test:  make SecondaryHomeApp && adb install -r -g
out/target/product/generic_x86/system/priv-app/SecondaryHomeApp/SecondaryHomeApp.apk
&& atest CarServiceTest

Change-Id: Ic72d240f90d5d25083de4a7d52c28d6ea7dfb470
diff --git a/tests/SecondaryHomeApp/src/com/android/car/secondaryhome/launcher/NotificationViewController.java b/tests/SecondaryHomeApp/src/com/android/car/secondaryhome/launcher/NotificationViewController.java
index 17f3b3c..ad096a6 100644
--- a/tests/SecondaryHomeApp/src/com/android/car/secondaryhome/launcher/NotificationViewController.java
+++ b/tests/SecondaryHomeApp/src/com/android/car/secondaryhome/launcher/NotificationViewController.java
@@ -52,14 +52,18 @@
      * Set handler to NotificationListener
      */
     public void enable() {
-        mCarNotificationListener.setHandler(mNotificationUpdateHandler);
+        if (mCarNotificationListener != null) {
+            mCarNotificationListener.setHandler(mNotificationUpdateHandler);
+        }
     }
 
     /**
      * Remove handler
      */
     public void disable() {
-        mCarNotificationListener.setHandler(null);
+        if (mCarNotificationListener != null) {
+            mCarNotificationListener.setHandler(null);
+        }
     }
 
     /**