Fix NPE in CellWidget.onBrowserEvent when cell does not consume any events

Fixes issue 7649.

Change-Id: I6d9b4979d7b68e7ff8fa652ab54635d2cc690fd9
Review-Link: https://gwt-review.googlesource.com/#/c/1721/

Review by: goktug@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@11486 8db76d5a-ed1c-0410-87a9-c151d255dfc7
diff --git a/user/src/com/google/gwt/user/cellview/client/CellWidget.java b/user/src/com/google/gwt/user/cellview/client/CellWidget.java
index a3bb819..f644cde 100644
--- a/user/src/com/google/gwt/user/cellview/client/CellWidget.java
+++ b/user/src/com/google/gwt/user/cellview/client/CellWidget.java
@@ -35,6 +35,8 @@
 import com.google.gwt.view.client.HasKeyProvider;
 import com.google.gwt.view.client.ProvidesKey;
 
+import java.util.Set;
+
 /**
  * A {@link Widget} that wraps a {@link Cell}.
  * 
@@ -193,7 +195,8 @@
 
     // Forward the event to the cell.
     String eventType = event.getType();
-    if (cell.getConsumedEvents().contains(eventType)) {
+    Set<String> consumedEvents = cell.getConsumedEvents();
+    if (consumedEvents != null && consumedEvents.contains(eventType)) {
       cell.onBrowserEvent(createContext(), getElement(), value, event, valueUpdater);
     }
   }