Index: wp-admin/custom-header.php
===================================================================
--- wp-admin/custom-header.php	(revision 23297)
+++ wp-admin/custom-header.php	(working copy)
@@ -1001,6 +1001,7 @@
 
 		$default = sprintf( $default, get_template_directory_uri(), get_stylesheet_directory_uri() );
 
+		$default_data = array();
 		foreach ( $this->default_headers as $header => $details ) {
 			if ( $details['url'] == $default ) {
 				$default_data = $details;