Make sure extra_query_vars is an array instead of an empty string to avoid weird bug that can cause all query vars to be stomped in certain envs.

git-svn-id: https://develop.svn.wordpress.org/trunk@2824 602fd350-edb4-49c9-b593-d223f7449a82

wp-includes/classes.php

@@ -1323,6 +1323,8 @@ class WP {
 
 		if (! empty($extra_query_vars))
 			parse_str($extra_query_vars, $extra_query_vars);
+		else
+			$extra_query_vars = array();
 
 		// Process PATH_INFO, REQUEST_URI, and 404 for permalinks.
 		if ((isset($_GET['error']) && $_GET['error'] == '404') ||
@@ -1537,4 +1539,4 @@ class WP {
 	}
 }
 
-?>
+?>