SystemUI: NotificationLockscreenUserManagerImpl: Avoid an NPE at boot

Log:
E AndroidRuntime: FATAL EXCEPTION: main
E AndroidRuntime: Process: com.android.systemui, PID: 2225
E AndroidRuntime: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.app.NotificationChannel.getLockscreenVisibility()' on a null object reference
E AndroidRuntime:        at com.android.systemui.statusbar.notification.interruption.KeyguardNotificationVisibilityProviderImpl.userSettingsDisallowNotification$disallowForUser(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:52)
E AndroidRuntime:        at com.android.systemui.statusbar.notification.interruption.KeyguardNotificationVisibilityProviderImpl.shouldHideNotification(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:32)
E AndroidRuntime:        at com.android.systemui.statusbar.notification.interruption.NotificationInterruptStateProviderImpl.canAlertCommon(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:74)
E AndroidRuntime:        at com.android.systemui.statusbar.notification.interruption.NotificationInterruptStateProviderWrapper.makeAndLogBubbleDecision(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:7)
E AndroidRuntime:        at com.android.systemui.wmshell.BubblesManager$5.onEntryAdded(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:7)
E AndroidRuntime:        at com.android.systemui.statusbar.notification.collection.notifcollection.EntryAddedEvent.dispatchToListener(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:3)
E AndroidRuntime:        at com.android.systemui.statusbar.notification.collection.NotifCollection.dispatchEvents(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:79)
E AndroidRuntime:        at com.android.systemui.statusbar.notification.collection.NotifCollection.dispatchEventsAndRebuildList(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:19)
E AndroidRuntime:        at com.android.systemui.statusbar.notification.collection.NotifCollection$1.onNotificationPosted(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:32)
E AndroidRuntime:        at com.android.systemui.statusbar.notification.collection.coalescer.GroupCoalescer$1.onNotificationPosted(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:179)
E AndroidRuntime:        at com.android.systemui.statusbar.NotificationListener$$ExternalSyntheticLambda1.run(go/retraceme f84293888a5b262147f0a1061d03f031c332b6e7a3d49333eb10588a5f8e9f5a:187)
...