protected <ReqT> Listener<ReqT> noOpCallListener() {
        return new Listener<ReqT>() {};
    }
Creates a new no-op call listener because you can neither return null nor throw an exception in
{@link #interceptCall(ServerCall, Metadata, ServerCallHandler)}.

@param <ReqT> The type of the request.
@return The newly created dummy listener.
grpc-server-spring-boot-starter/src/main/java/net/devh/boot/grpc/server/error/GrpcExceptionInterceptor.java