[MD Bookmarks] Clear drop indicator when dragging over invalid target.

chrome/browser/resources/md_bookmarks/dnd_manager.js

Index: chrome/browser/resources/md_bookmarks/dnd_manager.js
diff --git a/chrome/browser/resources/md_bookmarks/dnd_manager.js b/chrome/browser/resources/md_bookmarks/dnd_manager.js
index 4e6d879043e2bd832cb284b38ec8f7777c94c4b7..752c3cfd9129baed8005b7c17bdd1eb2bb1eafe5 100644
--- a/chrome/browser/resources/md_bookmarks/dnd_manager.js
+++ b/chrome/browser/resources/md_bookmarks/dnd_manager.js
@@ -477,8 +477,10 @@ cr.define('bookmarks', function() {
       // below based on mouse position etc.
       this.dropDestination_ =
           this.calculateDropDestination_(e.clientY, overElement);
-      if (!this.dropDestination_)
+      if (!this.dropDestination_) {
+        this.dropIndicator_.finish();
         return;
+      }
 
       if (e.dataTransfer) {
         e.dataTransfer.dropEffect =