Minor code cleanup

application/src/main/java/org/thingsboard/server/actors/device/DeviceActorMessageProcessor.java

@@ -95,12 +95,10 @@ public class DeviceActorMessageProcessor extends AbstractContextAwareMsgProcesso
     }
 
     private void refreshAttributes(DeviceAttributesEventNotificationMsg msg) {
-        if (this.deviceAttributes != null) {
-            if (msg.isDeleted()) {
-                msg.getDeletedKeys().forEach(key -> deviceAttributes.remove(key));
-            } else {
-                deviceAttributes.update(msg.getScope(), msg.getValues());
-            }
+        if (msg.isDeleted()) {
+            msg.getDeletedKeys().forEach(key -> deviceAttributes.remove(key));
+        } else {
+            deviceAttributes.update(msg.getScope(), msg.getValues());
         }
     }
 
@@ -206,7 +204,6 @@ public class DeviceActorMessageProcessor extends AbstractContextAwareMsgProcesso
     }
 
     void processAttributesUpdate(ActorContext context, DeviceAttributesEventNotificationMsg msg) {
-        //TODO: improve this procedure to fetch only changed attributes and support attributes deletion
         refreshAttributes(msg);
         Set<AttributeKey> keys = msg.getDeletedKeys();
         if (attributeSubscriptions.size() > 0) {

dao/src/main/java/org/thingsboard/server/dao/timeseries/SimpleListenableFuture.java

@@ -22,10 +22,6 @@ import com.google.common.util.concurrent.AbstractFuture;
  */
 public class SimpleListenableFuture<V> extends AbstractFuture<V> {
 
-    public SimpleListenableFuture() {
-
-    }
-
     public boolean set(V value) {
         return super.set(value);
     }