Client loses connection, then fails to reconnect

Summary

After a while, HipChat can lose connection, and will fail to automatically reconnect.

Environment

• Windows Client 4.0.1634+
• Windows Client 4.26.5.1655
• Windows Client 4.27.1.1658

Steps to Reproduce

1. Login to HipChat
2. After several hours, observe that HipChat lost connection

Expected Results

Client will automatically reconnect

Actual Results

Client will fail to connect, and display an error message

Logfiles will show messages like this:

[DEBUG] [Connection] OAuth timer expired. Fetching new OAuth token
[DEBUG] [AnalyticsDispatcher: analytics-event] {"name":"hipchat.client.oauth.token.refresh.requested","properties":{"reason":"Token expiry timer lapsed"}}
[ERROR] [Connection] Failed to fetch new OAuth token due to: TypeError: Cannot read property 'then' of undefined

Workaround

Restarting client, or logging out and logging back in again, establish a successful connection