Index: wp-includes/revision.php
===================================================================
--- wp-includes/revision.php	(revision 24396)
+++ wp-includes/revision.php	(working copy)
@@ -539,7 +539,7 @@
 function _wp_preview_meta_filter( $value, $object_id, $meta_key, $single ) {
 	$post = get_post();
 
-	if ( $post->ID != $object_id || ! in_array( $meta_key, _wp_post_revision_meta_keys() ) || 'revision' == $post->post_type )
+	if ( empty( $post ) || $post->ID != $object_id || ! in_array( $meta_key, _wp_post_revision_meta_keys() ) || 'revision' == $post->post_type )
 		return $value;
 
 	$preview = wp_get_post_autosave( $post->ID );