events: Always return valid settings objects in InputDeviceSettingsEvdev

Bug: b/241965700
Change-Id: I630cb92810ee7f2505941c1954f9ce9fbfda6d16
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4334945


Commit-Queue: David Padlipsky <dpad@google.com>
Reviewed-by: Sean O'Brien <seobrien@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1118906}