Fix NPE in updateScreenshot

 Bug: 3448395

Change-Id: I69ab59597735d26c2881fc7f3d48b0a115bb2547
diff --git a/src/com/android/browser/Controller.java b/src/com/android/browser/Controller.java
index 6393ac8..6b72c25 100644
--- a/src/com/android/browser/Controller.java
+++ b/src/com/android/browser/Controller.java
@@ -1970,6 +1970,10 @@
         // currently accessible here.
 
         WebView view = tab.getWebView();
+        if (view == null) {
+            // Tab was destroyed
+            return;
+        }
         final String url = tab.getUrl();
         final String originalUrl = view.getOriginalUrl();