Add null check

 Bug: 4094190

Change-Id: I8af2db0764ab5c103dd5d25ad6457c4e05e4b06c
diff --git a/src/com/android/browser/BrowserBookmarksPage.java b/src/com/android/browser/BrowserBookmarksPage.java
index 98b25a8..de28d0d 100644
--- a/src/com/android/browser/BrowserBookmarksPage.java
+++ b/src/com/android/browser/BrowserBookmarksPage.java
@@ -453,7 +453,7 @@
     }
 
     private void loadUrl(int position) {
-        if (mCallbacks != null) {
+        if (mCallbacks != null && mAdapter != null) {
             mCallbacks.onBookmarkSelected(mAdapter.getItem(position), false);
         }
     }