KeyguardUpdateMonitor: Add missing getFaceAuthInteractor null check

Fixes commit 5e49307013cf55d0e37628b55d84ef71b4855d47

Flag: EXEMPT bugfix
Test: unfold foldable device without face auth.
Change-Id: Idbfab8dbe671bfd6b992f5945d6636e99feccbc4
diff --git a/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitor.java b/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitor.java
index 7f5839d4..057fb68 100644
--- a/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitor.java
+++ b/packages/SystemUI/src/com/android/keyguard/KeyguardUpdateMonitor.java
@@ -1873,7 +1873,9 @@
                     if (posture == DEVICE_POSTURE_OPENED) {
                         mLogger.d("Posture changed to open - attempting to request active"
                                 + " unlock and run face auth");
-                        getFaceAuthInteractor().onDeviceUnfolded();
+                        if (getFaceAuthInteractor() != null) {
+                            getFaceAuthInteractor().onDeviceUnfolded();
+                        }
                         requestActiveUnlockFromWakeReason(PowerManager.WAKE_REASON_UNFOLD_DEVICE,
                                 false);
                     }