Fix Rich Presence Nulling

[Aluerie]

Summary

Just a small PR out of #help thread.

TL;DR for posterity

This PR fixes a bug where rich_presence attribute for user classes would reset its value to None if the incoming proto doesn't have rich_presence field set which occasionally does happen.

Checklist

• [X] If code changes were made then they have been tested.
  • [ ] I have updated the documentation to reflect the changes.
• [X] This PR fixes an issue.
• [ ] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)

[Gobot1234]

Thank you!