updated comment, fixed ctx data changing

application/src/main/java/org/thingsboard/server/service/subscription/DefaultTbEntityDataSubscriptionService.java

@@ -725,11 +725,12 @@ public class DefaultTbEntityDataSubscriptionService implements TbEntityDataSubsc
                             update = new EntityDataUpdate(ctx.getCmdId(), ctx.getData(), null, ctx.getMaxEntitiesPerDataSubscription());
                             ctx.setInitialDataSent(true);
                         } else {
-                            // to avoid updating timeseries with empty values
-                            List<EntityData> data = ctx.getData().getData().stream()
-                                    .peek(entityData -> entityData.setTimeseries(null))
+                            // if ctx has timeseries subscription, timeseries values are cleared after each update and is empty in ctx data,
+                            // so to avoid sending timeseries update with empty map we set it to null
+                            List<EntityData> preparedData = ctx.getData().getData().stream()
+                                    .map(entityData -> new EntityData(entityData.getEntityId(), entityData.getLatest(), null))
                                     .toList();
-                            update = new EntityDataUpdate(ctx.getCmdId(), null, data, ctx.getMaxEntitiesPerDataSubscription());
+                            update = new EntityDataUpdate(ctx.getCmdId(), null, preparedData, ctx.getMaxEntitiesPerDataSubscription());
                         }
                         ctx.sendWsMsg(update);
                     } finally {