Fix monkey NPE

    Bug: 6354353

Change-Id: Ia5da9c5842312b7ef726a73da669425256bca2a4
diff --git a/src/com/android/browser/PageDialogsHandler.java b/src/com/android/browser/PageDialogsHandler.java
index 19cbfcd..3ed1004 100644
--- a/src/com/android/browser/PageDialogsHandler.java
+++ b/src/com/android/browser/PageDialogsHandler.java
@@ -137,6 +137,7 @@
     void showPageInfo(final Tab tab,
             final boolean fromShowSSLCertificateOnError,
             final String urlCertificateOnError) {
+        if (tab == null) return;
         final LayoutInflater factory = LayoutInflater.from(mContext);
 
         final View pageInfoView = factory.inflate(R.layout.page_info, null);