[TECHNICAL SUPPORT] LPS-49461 The Profile Pictures of the Users is no longer displayed by Chat

https://issues.liferay.com/browse/LPS-49461

Hi Nate,

I decided to make more changes in the backend to
- ensure we use the appropriate default portrait image when the user doesn't set a custom one
- avoid querying the user object (again) in ChatPollerProcessor

FYI: I'll take care of this issue while Norbi @NorbertKocsis is OOO (till September 1st.).

Let me know if you was wrong any point.

Thanks,
Tibor