Fix a null pointer exception.

In setTitleAndUrl, check to make sure url is non null before
calling url.toString().
diff --git a/src/com/android/browser/TitleBar.java b/src/com/android/browser/TitleBar.java
index fdcab3c..b818dd2 100644
--- a/src/com/android/browser/TitleBar.java
+++ b/src/com/android/browser/TitleBar.java
@@ -137,7 +137,10 @@
         } else {
             mTitle.setText(title);
         }
-        mUrl.setText(BrowserActivity.buildTitleUrl(url.toString()));
+        if (url != null) {
+            url = BrowserActivity.buildTitleUrl(url.toString());
+        }
+        mUrl.setText(url);
     }
 
     /* package */ void setToTabPicker() {