@Nullable
    static Throwable responseCause(ServiceRequestContext ctx) {
        final RequestLogAccess log = ctx.log();
        if (log.isAvailable(RequestLogProperty.RESPONSE_CAUSE)) {
            return log.partial().responseCause();
        } else {
            return null;
        }
    }
Ensure that unframedGrpcStatusMappingFunction never returns null by falling back to the default.
grpc/src/main/java/com/linecorp/armeria/server/grpc/UnframedGrpcErrorHandlerUtil.java