[keyserver] Handle null browser detection result
Summary:
When a browser can't be detected we need to make sure that we don't crash. Handling this case in the same way as if it was a web browser probably makes the most sense.
Depends on D13587
Test Plan: Replaced detectionResult with null and checked that we're handling it as if it was a web browser.
Reviewers: kamil, inka
Reviewed By: kamil
Subscribers: ashoat
Differential Revision: https://phab.comm.dev/D13588