Add null check

 Bug: 5452795

Change-Id: I8b43875e0e72665384c974c502d8f38946f0c6f1
diff --git a/src/com/android/browser/PhoneUi.java b/src/com/android/browser/PhoneUi.java
index b0f3d74..37370e5 100644
--- a/src/com/android/browser/PhoneUi.java
+++ b/src/com/android/browser/PhoneUi.java
@@ -521,6 +521,9 @@
         }
 
         public void set(TitleBar tbar, WebView web) {
+            if (tbar == null || web == null) {
+                return;
+            }
             if (tbar.getWidth() > 0 && tbar.getEmbeddedHeight() > 0) {
                 if (mTitleBarBitmap == null
                         || mTitleBarBitmap.getWidth() != tbar.getWidth()