Don't crash when extra logging is enabled.

Change-Id: I76cf8db0f51ed33e91acee9636180e8d7c0b5ff9
diff --git a/services/java/com/android/server/PackageManagerService.java b/services/java/com/android/server/PackageManagerService.java
index f5862df..e3480a8 100644
--- a/services/java/com/android/server/PackageManagerService.java
+++ b/services/java/com/android/server/PackageManagerService.java
@@ -2022,7 +2022,11 @@
                     ActivityInfo ai = getActivityInfo(pa.mActivity, flags);
                     if (DEBUG_PREFERRED) {
                         Log.v(TAG, "Got preferred activity:");
-                        ai.dump(new LogPrinter(Log.INFO, TAG), "  ");
+                        if (ai != null) {
+                            ai.dump(new LogPrinter(Log.VERBOSE, TAG), "  ");
+                        } else {
+                            Log.v(TAG, "  null");
+                        }
                     }
                     if (ai != null) {
                         for (int j=0; j<N; j++) {