Fix Validator initialization with a no-op implementation

Issue: SPR-11185

spring-messaging/src/main/java/org/springframework/messaging/simp/annotation/support/SimpAnnotationMethodMessageHandler.java

@@ -54,6 +54,7 @@ import org.springframework.util.AntPathMatcher;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
 import org.springframework.util.PathMatcher;
+import org.springframework.validation.Errors;
 import org.springframework.validation.Validator;
 
 /**
@@ -243,7 +244,8 @@ public class SimpAnnotationMethodMessageHandler extends AbstractMethodMessageHan
 		resolvers.add(new MessageMethodArgumentResolver());
 
 		resolvers.addAll(getCustomArgumentResolvers());
-		resolvers.add(new PayloadArgumentResolver(this.messageConverter, this.validator));
+		resolvers.add(new PayloadArgumentResolver(this.messageConverter,
+				this.validator != null ? this.validator : new NoopValidator()));
 
 		return resolvers;
 	}
@@ -360,4 +362,14 @@ public class SimpAnnotationMethodMessageHandler extends AbstractMethodMessageHan
 		return new AnnotationExceptionHandlerMethodResolver(beanType);
 	}
 
+	private static final class NoopValidator implements Validator {
+		@Override
+		public boolean supports(Class<?> clazz) {
+			return false;
+		}
+		@Override
+		public void validate(Object target, Errors errors) {
+		}
+	};
+
 }