[User Switcher] Fix IllegalStateException in...

The UserInteractor. In some cases, we maybe be returning null when we
are mapping the userinfo to the usermodel. I've added a try catch into
this collector and separated out the filter and map behavior of the
function into two separate methods.

Fixes: 255446308
Test: Tests seem to be unaffected by the change.
Test: Switch to secondary user and restart and open full screen user
switcher.
Test: Open full screen user switcher from primary user, secondary user,
and guest user.

Change-Id: I5fc82055488132bec5923eb4dbfaac4f8b6eaa93