KeyguardPreviewSmartspaceViewBinder: Fix NPE

When Smartspace is not enabled, largeDateView is null.
Google seems to have forgotten to add a null check here like
they did to other usages of largeDateView.

E AndroidRuntime: FATAL EXCEPTION: main
E AndroidRuntime: Process: com.android.systemui, PID: 7338
E AndroidRuntime: java.lang.NullPointerException: Attempt to invoke virtual method 'int android.view.View.getId()' on a null object reference
E AndroidRuntime: 	at com.android.systemui.keyguard.ui.binder.KeyguardPreviewSmartspaceViewBinder$bind$1$1$1$4.emit(KeyguardPreviewSmartspaceViewBinder.kt:129)
E AndroidRuntime: 	at com.android.systemui.keyguard.ui.binder.KeyguardPreviewSmartspaceViewBinder$bind$1$1$1$4.emit(KeyguardPreviewSmartspaceViewBinder.kt:66)

Change-Id: Iff1bfdaab16a36af6e1b115ac90f02b735d05701
Signed-off-by: ExtremeXT <extremextdev@gmail.com>