Fix participant no access when single participant

[ashleysmithTTD]

Quick bug fix to show something different than the Participant Switcher if the user navigates to a participant they don't have access to, but only belong to one participant.

Test Plan:

• Make sure navigation with the switcher still works when a user has multiple participans
• Update your user to only have access to one participant and check the UX when navigating to a participant in the URL that doesn't exist or they don't have access to (example: http://localhost:3000/participant/123333/home)