Attributes: revert returning null for non-elements

src/attributes/attr.js

@@ -31,7 +31,7 @@ jQuery.extend({
 
 		// don't get/set attributes on text, comment and attribute nodes
 		if ( !elem || nType === 3 || nType === 8 || nType === 2 ) {
-			return null;
+			return;
 		}
 
 		// Fallback to prop when attributes are not supported

test/unit/attributes.js

@@ -371,7 +371,7 @@ test( "attr(String, Object)", function() {
 	jQuery.each( [ commentNode, textNode, attributeNode ], function( i, elem ) {
 		var $elem = jQuery( elem );
 		$elem.attr( "nonexisting", "foo" );
-		strictEqual( $elem.attr("nonexisting"), null, "attr(name, value) works correctly on comment and text nodes (bug #7500)." );
+		strictEqual( $elem.attr("nonexisting"), undefined, "attr(name, value) works correctly on comment and text nodes (bug #7500)." );
 	});
 
 	jQuery.each( [ window, document, obj, "#firstp" ], function( i, elem ) {