Default to 404 code for RouteNotFoundException

Just want to get Stratigility’s FinalHandler showing something more apt
than “Internal server error”

framework/core/src/Http/RouteNotFoundException.php

@@ -6,4 +6,8 @@ use Exception;
 
 class RouteNotFoundException extends Exception
 {
+    public function __construct($message = null, $code = 404, Exception $previous = null)
+    {
+        parent::__construct($message, $code, $previous);
+    }
 }