this is the way to do it

Author: moritztim

addons/form/nodes/Validators/StringValidator.gd

@@ -95,8 +95,7 @@ func validate(
 	## Text to validate
 	subject
 ) -> bool:
-	if !(subject is String):
-		return
+	subject = subject as String
 	super.validate(subject)
 	var _regex := RegEx.new()