Incorrect number of online users in the channel

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(This may be related to issue #68.)

The number of online users shown next to a talk name does not match the number shown in the top right corner of the chat room for that talk. I believe the number next to the talk name is incorrect.

Steps to reproduce:
1. (Web) Enter a chatroom. The count next to the talk name in the sidebar increments by 1. So does the count shown in the chat room itself.
2. (iOS) Enter the same chatroom from the iOS app. Since you're entering as the same user, the count should not increment. The count shown within the chat room correctly shows that. However, in the sidebar, next to the talk name, the count gets incremented by 1 again (therefore counting yourself twice).

Start by reproducing the count in a web chatroom and then enter the same talk from iOS, comparing the sidebar value with the count in the chat room. Check the related issue #68 for context. Done means the same user is counted only once in both locations.

Written by the indexing model from the issue text.