Index: src/wp-admin/widgets.php
===================================================================
--- src/wp-admin/widgets.php	(revision 36000)
+++ src/wp-admin/widgets.php	(working copy)
@@ -422,7 +422,7 @@
 
 							submit_button( __( 'Clear Inactive Widgets' ), 'delete', 'removeinactivewidgets', false, $attributes );
 							?>
-							<span class="spinner">
+							<span class="spinner"></span>
 						</p>
 						<?php wp_nonce_field( 'remove-inactive-widgets', '_wpnonce_remove_inactive_widgets' ); ?>
 					</form>