KeyguardUpdateMonitor: Add missing getFaceAuthInteractor null check

Fixes commit 5e49307013cf55d0e37628b55d84ef71b4855d47

Flag: EXEMPT bugfix
Test: unfold foldable device without face auth.
Change-Id: Idbfab8dbe671bfd6b992f5945d6636e99feccbc4
1 file changed