Ignore null action in VirtualizationSystemService$Receiver.

Bug: 376388058
Test: Manual.
Change-Id: I941393567d939b82cb031ed18380b1bb0db77fad
diff --git a/libs/service-virtualization/src/com/android/system/virtualmachine/VirtualizationSystemService.java b/libs/service-virtualization/src/com/android/system/virtualmachine/VirtualizationSystemService.java
index 998389b..afa286c 100644
--- a/libs/service-virtualization/src/com/android/system/virtualmachine/VirtualizationSystemService.java
+++ b/libs/service-virtualization/src/com/android/system/virtualmachine/VirtualizationSystemService.java
@@ -120,7 +120,12 @@
 
         @Override
         public void onReceive(Context context, Intent intent) {
-            switch (intent.getAction()) {
+            final String action = intent.getAction();
+            if (action == null) {
+                return;
+            }
+
+            switch (action) {
                 case Intent.ACTION_USER_REMOVED:
                     onUserRemoved(intent);
                     break;
@@ -128,7 +133,7 @@
                     onPackageRemoved(intent);
                     break;
                 default:
-                    Log.e(TAG, "received unexpected intent: " + intent.getAction());
+                    Log.e(TAG, "received unexpected intent: " + intent);
                     break;
             }
         }