Closing a session, immediately after it's been opened, throws an error

[sorsaffari]

Description

Closing a session, immediately after it's been opened, throws:
(node:57100) UnhandledPromiseRejectionWarning: Error: 2 UNKNOWN: null

Environment

1. OS (where Grakn server runs): Mac OS 10.14.2
2. Grakn version (and platform): 1.5.0 SNAPSHOT
3. Grakn client-nodejs version: 1.5.0 SNAPSHOT
4. Node.js version: 10.12.0

Reproducible Steps

Steps to create the smallest reproducible scenario:
index.js:

const Grakn = require("grakn-client");

openSession("social_network");

async function openSession (keyspace) {
    const client = new Grakn("localhost:48555");
    const session = await client.session(keyspace);
    await session.close();
};

run: node index

Expected Output

nothing to be logged into the terminal.

Actual Output

(node:57100) UnhandledPromiseRejectionWarning: Error: 2 UNKNOWN: null. Please check server logs for the stack trace.
    at Object.exports.createStatusError (/Users/soroushsaffari/tests/jclient/node_modules/grpc/src/common.js:91:15)
    at Object.onReceiveStatus (/Users/soroushsaffari/tests/jclient/node_modules/grpc/src/client_interceptors.js:1204:28)
    at InterceptingListener._callNext (/Users/soroushsaffari/tests/jclient/node_modules/grpc/src/client_interceptors.js:568:42)
    at InterceptingListener.onReceiveStatus (/Users/soroushsaffari/tests/jclient/node_modules/grpc/src/client_interceptors.js:618:8)
    at callback (/Users/soroushsaffari/tests/jclient/node_modules/grpc/src/client_interceptors.js:845:24)
(node:57100) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:57100) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

Additional information

if the session is used to create a transaction, followed by closing the transaction, no errors get thrown:

const Grakn = require("grakn-client");

openSession("social_network");

async function openSession (keyspace) {
    const client = new Grakn("localhost:48555");
    const session = await client.session(keyspace);
    const transaction = await session.transaction(Grakn.txType.READ);
    await transaction.close();
    await session.close();
};