Fixed regexp for named route

Author: Alessandro Manias

lib/util/named-group-regexp.js

@@ -14,7 +14,7 @@ const pattern = [
 	'[>\']',
 	// Get everything up to the end of the capture group: this is the RegExp used
 	// when matching URLs to this route, which we can use for validation purposes.
-	'([^\\)]*)',
+	'([^\\)]*(\))?)\??)',
 	// Capture group end
 	'\\)',
 ].join( '' );