Can't find the reason for the redundant nullcheck of this, which is not known to be null

In Sonar, I see a redundant nullcheck of this, which is known to be a non-null error, but I cannot find a reason for this.

Hope can help me find the reason.

thanks and regards

Edit1:

    public class Filter extends AbstractBaseEntity implements Serializable {
    public Filter() {
        super();
    }
}

      

        
        
        
      

    

AbstractBaseEntity has no implemented constructor