Client side player.id is appended with `NaN` after interpolation

[EmersonYe]

Summary:

NaN is appended to player.id on the client-side after interpolation. This happens after the second update is received from the server (i.e. the first time interpolation is performed).

Steps to reproduce:

1. Add console.log(me.id); to the start of the render() function in src/client/render.js.
2. Start the server with npm run develop from the command line.
3. Visit localhost:3000.
4. Open dev tools (ctrl + shift + j on Windows).
5. Join the game by clicking on PLAY.

Expected results:

My socket id (e.g. ljLSqzmUSc5ZGEf5AAAC) is logged to console repeatedly.

Actual results:

1. My socket id is logged to console 6 times (e.g. ljLSqzmUSc5ZGEf5AAAC).
2. My socket id appended with NaN (e.g. ljLSqzmUSc5ZGEf5AAACNaN) is logged to console repeatedly.

Additional information:

I encountered this bug when trying to implement a chat feature. Each chat object had a reference to it's parentId without NaN appended to it. I was unable to match chat objects to players in the render() function in src/client/render.js because the player id's had changed to have NaN appended to them.