There's also another issue that, after you attempt you upload a local avatar, the Okay button doesn't work, though the Cancel button still does.
Here are the steps to reproduce this:
- Open the Avatar Editor overlay
- Select Upload new custom avatar if it is not already selected
- Click on Choose File and choose an avatar of your choice
- Notice the current avatar does not change
- Okay button now does not work
If it's of use, I'm on Windows 10 using Chrome.