Summary: Ref T7126. Dictionaries do not have a `length` property unlike arrays resulting in the `getActiveListenerCount()` function returning undefined results. Using the `length` property on the array of keys will work.
Test Plan: Using `wscat` to generate multiple connections to the server, establish new ones and close others while keeping an eye on the displayed `clients.active` value.
Reviewers: epriestley, #blessed_reviewers
Reviewed By: epriestley, #blessed_reviewers
Subscribers: Korvin, epriestley
Maniphest Tasks: T7126
Differential Revision: https://secure.phabricator.com/D11647
a424fec7bb