Index: wp-admin/includes/post.php
===================================================================
--- wp-admin/includes/post.php	(revision 18073)
+++ wp-admin/includes/post.php	(working copy)
@@ -1649,7 +1649,7 @@
 			$val = $v ? 'true' : 'false';
 			$mce_options .= $k . ':' . $val . ', ';
 			continue;
-		} elseif ( is_string($v) && ( ('{' == $v{0} && '}' == $v{strlen($v) - 1}) || ('[' == $v{0} && ']' == $v{strlen($v) - 1}) || preg_match('/^\(?function ?\(/', $v) ) ) {
+		} elseif ( !empty($v) && is_string($v) && ( ('{' == $v{0} && '}' == $v{strlen($v) - 1}) || ('[' == $v{0} && ']' == $v{strlen($v) - 1}) || preg_match('/^\(?function ?\(/', $v) ) ) {
 			$mce_options .= $k . ':' . $v . ', ';
 			continue;
 		}