Fix annotation of getBehavior

Change-Id: Ie28d4cff39b57ae648deac410a91dcd4ecbe6954
diff --git a/design/src/android/support/design/widget/CoordinatorLayout.java b/design/src/android/support/design/widget/CoordinatorLayout.java
index c801ad6..7173b6b 100644
--- a/design/src/android/support/design/widget/CoordinatorLayout.java
+++ b/design/src/android/support/design/widget/CoordinatorLayout.java
@@ -2553,7 +2553,7 @@
          *
          * @return The current behavior or null if no behavior is specified
          */
-        @NonNull
+        @Nullable
         public Behavior getBehavior() {
             return mBehavior;
         }