What is the proper way of checking if the entity is already removed?

EntityListener handles when the entity is added or removed. My problem is when I remove the entity from the engine, while this entity is being used as Component owner, it cause a java.lang.NullPointerException. I wonder what method to use to check if entity is already removed from the engine.

For example:

public class PoliceComponent implements Component {
    public Entity criminal;
}

engine.removeEntity(entity)

PoliceComponent police ...
Vector2 criminalPos = Mapper.transform.get(police.criminal).position; 
// Now this line will cause an error

Question : is there a method like this to check for entity existence? or something better safer to remove entity while is in use.

    if (engine.hasEntity(entity)) {
          // exists
    }

Start by reading EntityListener and the engine.removeEntity call, then trace the Mapper.transform.get(police.criminal) access shown in the example. Determine the supported entity lifecycle and safe handling for components that retain removed entities; done means the behavior and recommended approach are documented or covered by a focused regression test.