Attributes: return empty array for select-multiple with no values

Fixes gh-2562
Close gh-2689

src/attributes/val.js

@@ -90,7 +90,7 @@ jQuery.extend( {
 				var value, option,
 					options = elem.options,
 					index = elem.selectedIndex,
-					one = elem.type === "select-one" || index < 0,
+					one = elem.type === "select-one",
 					values = one ? null : [],
 					max = one ? index + 1 : options.length,
 					i = index < 0 ?