Index: wp-includes/query.php
===================================================================
--- wp-includes/query.php	(revision 17389)
+++ wp-includes/query.php	(working copy)
@@ -1837,7 +1837,7 @@
 	 * @return mixed
 	 */
 	function get($query_var) {
-		if ( isset($this->query_vars[$query_var]) )
+		if ( array_key_exists($query_var, $this->query_vars) )
 			return $this->query_vars[$query_var];
 
 		return '';