Spring Cloud Openfeign Null in SpEL expressions not resolved correctly for @FeignClient attributes

Describe the bug @FeignClient(url = "${test.url:#{null}}", name = "testRest") if env not set test.url variable , the url for create feign client is "null" string, may this should be null

https://github.com/spring-cloud/spring-cloud-openfeign/blob/60b55c7b068f7411996aa215475efd6e853bbcf6/spring-cloud-openfeign-core/src/main/java/org/springframework/cloud/openfeign/FeignClientsRegistrar.java#L305 may should be

        Object evaluateValue = resolver.evaluate(resolved,
            new BeanExpressionContext(beanFactory, null));
        if (evaluateValue!=null){
            return String.valueOf(evaluateValue);
        }
        return null;

Comment From: OlgaMaciaszek

Hello, @ilumer. Thanks for submitting this. Makes sense.