Suppress warning about unchecked cast

Change-Id: I9311529541932dd3c95a43985e50d40c67801a15
diff --git a/src/main/java/com/google/gwtorm/nosql/generic/GenericAccess.java b/src/main/java/com/google/gwtorm/nosql/generic/GenericAccess.java
index edd92e8..cdaa4f5 100644
--- a/src/main/java/com/google/gwtorm/nosql/generic/GenericAccess.java
+++ b/src/main/java/com/google/gwtorm/nosql/generic/GenericAccess.java
@@ -454,6 +454,7 @@
     encodePrimaryKey(b, key);
 
     try {
+      @SuppressWarnings("unchecked")
       final T[] res = (T[]) new Object[3];
       db.atomicUpdate(b.toByteArray(), new AtomicUpdate<byte[]>() {
         @Override