avoid NPE accessing location manager, event center and notification center

src/main/java/org/thoughtcrime/securesms/ApplicationContext.java

@@ -62,9 +62,9 @@ public class ApplicationContext extends MultiDexApplication {
   private Rpc                    rpc;
   private DcContext              dcContext;
 
-  public DcLocationManager      dcLocationManager;
-  public DcEventCenter          eventCenter;
-  public NotificationCenter     notificationCenter;
+  private DcLocationManager      dcLocationManager;
+  private DcEventCenter          eventCenter;
+  private NotificationCenter     notificationCenter;
   private JobManager            jobManager;
 
   private int                   debugOnAvailableCount;
@@ -127,6 +127,33 @@ public class ApplicationContext extends MultiDexApplication {
     }
   }
 
+  /**
+   * Get DcLocationManager instance, waiting for initialization if necessary.
+   * This method is thread-safe and will block until initialization is complete.
+   */
+  public DcLocationManager getLocationManager() {
+    ensureInitialized();
+    return dcLocationManager;
+  }
+
+  /**
+   * Get DcEventCenter instance, waiting for initialization if necessary.
+   * This method is thread-safe and will block until initialization is complete.
+   */
+  public DcEventCenter getEventCenter() {
+    ensureInitialized();
+    return eventCenter;
+  }
+
+  /**
+   * Get NotificationCenter instance, waiting for initialization if necessary.
+   * This method is thread-safe and will block until initialization is complete.
+   */
+  public NotificationCenter getNotificationCenter() {
+    ensureInitialized();
+    return notificationCenter;
+  }
+
   @Override
   public void onCreate() {
     super.onCreate();
@@ -187,14 +214,13 @@ public class ApplicationContext extends MultiDexApplication {
           dcContext = dcAccounts.getSelectedAccount();
           notificationCenter = new NotificationCenter(this);
           eventCenter = new DcEventCenter(this);
+          dcLocationManager = new DcLocationManager(this, dcContext);
 
           // Mark as initialized before starting threads that depend on it
           isInitialized = true;
           initLock.notifyAll();
           Log.i(TAG, "DcAccounts initialization complete");
 
-          dcLocationManager = new DcLocationManager(this); // depends on dcContext
-
           new Thread(() -> {
               Log.i(TAG, "Starting event loop");
               DcEventEmitter emitter = dcAccounts.getEventEmitter();

src/main/java/org/thoughtcrime/securesms/connect/DcHelper.java

@@ -77,11 +77,11 @@ public class DcHelper {
     }
 
     public static DcEventCenter getEventCenter(@NonNull Context context) {
-        return ApplicationContext.getInstance(context).eventCenter;
+        return ApplicationContext.getInstance(context).getEventCenter();
     }
 
     public static NotificationCenter getNotificationCenter(@NonNull Context context) {
-        return ApplicationContext.getInstance(context).notificationCenter;
+        return ApplicationContext.getInstance(context).getNotificationCenter();
     }
 
     public static boolean isConfigured(Context context) {

src/main/java/org/thoughtcrime/securesms/geolocation/DcLocationManager.java

@@ -16,6 +16,8 @@ import java.util.Observer;
 
 import static android.content.Context.BIND_AUTO_CREATE;
 
+import com.b44t.messenger.DcContext;
+
 public class DcLocationManager implements Observer {
 
     private static final String TAG = DcLocationManager.class.getSimpleName();
@@ -40,10 +42,10 @@ public class DcLocationManager implements Observer {
         }
     };
 
-    public DcLocationManager(Context context) {
+    public DcLocationManager(Context context, DcContext dcContext) {
         this.context = context.getApplicationContext();
         DcLocation.getInstance().addObserver(this);
-        if (DcHelper.getContext(context).isSendingLocationsToChat(0)) {
+        if (dcContext.isSendingLocationsToChat(0)) {
             startLocationEngine();
         }
     }

src/main/java/org/thoughtcrime/securesms/mms/AttachmentManager.java

@@ -473,7 +473,7 @@ public class AttachmentManager {
 
   public static void selectLocation(Activity activity, int chatId) {
     ApplicationContext applicationContext = ApplicationContext.getInstance(activity);
-    DcLocationManager dcLocationManager = applicationContext.dcLocationManager;
+    DcLocationManager dcLocationManager = applicationContext.getLocationManager();
 
     if (DcHelper.getContext(applicationContext).isSendingLocationsToChat(chatId)) {
       dcLocationManager.stopSharingLocation(chatId);