fix: Node Issues (#2498)

- Allow adding new nodes without port
- Replace default port number for empty string when there's no port added

lib/core/node_port_validator.dart

@@ -4,8 +4,10 @@ import 'package:cake_wallet/core/validator.dart';
 class NodePortValidator extends TextValidator {
   NodePortValidator()
       : super(
-            errorMessage: S.current.error_text_node_port,
-            minLength: 0,
-            maxLength: 5,
-            pattern: '^[0-9]');
+          errorMessage: S.current.error_text_node_port,
+          minLength: 0,
+          maxLength: 5,
+          pattern: '^[0-9]',
+          isAutovalidate: true,
+        );
 }