Version 5.0.0 beta 4

system/Content/Api/ItemController.php

@@ -165,7 +165,7 @@ class ItemController extends Controller
 		
 		/* Sort */
 		$supportedSortBy = array( 'date', 'title' );
-		if( $class::$databaseColumnMap['updated'] )
+		if( isset($class::$databaseColumnMap['updated'] ) )
 		{
 			$supportedSortBy[] = 'updated';
 		}