Var wasn't being explicitly declared. Fixes #7226.

Author: jeresig

src/core.js

@@ -312,7 +312,7 @@ jQuery.fn.init.prototype = jQuery.fn;
 
 jQuery.extend = jQuery.fn.extend = function() {
 	// copy reference to target object
-	var target = arguments[0] || {}, i = 1, length = arguments.length, deep = false, options, name, src, copy, copyIsArray;
+	var target = arguments[0] || {}, i = 1, length = arguments.length, deep = false, options, name, src, copy, copyIsArray, clone;
 
 	// Handle a deep copy situation
 	if ( typeof target === "boolean" ) {