`openapi:ServiceInfo` annotation is not working properly for nil values

[SasinduDilshara]

import ballerina/openapi;
import ballerina/http;

@openapi:ServiceInfo {
    'version: ()
}
service /sales0 on new http:Listener(9505) {
}

In here the ballerina-openapi tool will read the version as string representation of(). It should be null