Do not destroy the life cycle when the user is invalid.

components/proximity_auth/proximity_auth_system.cc

Index: components/proximity_auth/proximity_auth_system.cc
diff --git a/components/proximity_auth/proximity_auth_system.cc b/components/proximity_auth/proximity_auth_system.cc
index 3386f14e5123ae06d6bf70001cf14e969924316d..f2b9d40957c66f35ac06c764dfd766e16e68fbe7 100644
--- a/components/proximity_auth/proximity_auth_system.cc
+++ b/components/proximity_auth/proximity_auth_system.cc
@@ -117,7 +117,10 @@ void ProximityAuthSystem::OnLifeCycleStateChanged(
 
 void ProximityAuthSystem::OnScreenDidLock(
     ScreenlockBridge::LockHandler::ScreenType screen_type) {
-  OnFocusedUserChanged(ScreenlockBridge::Get()->focused_account_id());
+  const AccountId& focused_account_id =
+      ScreenlockBridge::Get()->focused_account_id();
+  if (focused_account_id.is_valid())
+    OnFocusedUserChanged(focused_account_id);
 }
 
 void ProximityAuthSystem::OnScreenDidUnlock(