Fix small issue in sync_disable_observer.cc.

IsUsingSecondaryPassphrase() shouldn't be called if sync service
isn't initialized, according to its docs.

BUG=792104

Change-Id: I6320d7cfed2dfe924ef99f2d5d87c6579347bd9a
Reviewed-on: https://chromium-review.googlesource.com/809190Reviewed-by: Bryan McQuade <bmcquade@chromium.org>
Commit-Queue: Alexei Svitkine <asvitkine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521776}

components/ukm/observers/sync_disable_observer.cc

@@ -16,11 +16,12 @@ SyncDisableObserver::~SyncDisableObserver() {}
 // static
 SyncDisableObserver::SyncState SyncDisableObserver::GetSyncState(
     syncer::SyncService* sync_service) {
+  const bool initialized = sync_service->IsEngineInitialized();
   return SyncDisableObserver::SyncState{
       sync_service->GetPreferredDataTypes().Has(
           syncer::HISTORY_DELETE_DIRECTIVES),
-      sync_service->IsEngineInitialized(),
-      sync_service->IsUsingSecondaryPassphrase(),
+      initialized,
+      initialized ? sync_service->IsUsingSecondaryPassphrase() : false,
   };
 }