Index: wp-includes/js/autosave.dev.js
===================================================================
--- wp-includes/js/autosave.dev.js	(revision 19471)
+++ wp-includes/js/autosave.dev.js	(working copy)
@@ -283,11 +283,11 @@
 	}
 
 	if ( fullscreen && fullscreen.settings.visible ) {
-		post_data["post_title"] = jQuery('#wp-fullscreen-title').val();
-		post_data["content"] = jQuery("#wp_mce_fullscreen").val();
+		post_data["post_title"] = jQuery('#wp-fullscreen-title').val() || '';
+		post_data["content"] = jQuery("#wp_mce_fullscreen").val() || '';
 	} else {
-		post_data["post_title"] = jQuery("#title").val()
-		post_data["content"] = jQuery("#content").val();
+		post_data["post_title"] = jQuery("#title").val() || '';
+		post_data["content"] = jQuery("#content").val() || '';
 	}
 
 	if ( jQuery('#post_name').val() )