Fix NullPointerException in DeviceAuthenticatorControllerImpl

It's possible that biometricManager would be null in canAuthenticate
(though it should be rare). So a check for null is needed and an error
is returned in that case.

Bug: 366386611
Change-Id: I766bfccb8f775d332f0bf6345c2827218cda3d93
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5904095
Reviewed-by: Ioana Pandele <ioanap@chromium.org>
Commit-Queue: Anna Tsvirchkova <atsvirchkova@google.com>
Cr-Commit-Position: refs/heads/main@{#1362964}