java.lang.IllegalArgumentException: Cannot add a null child view to a ViewGroup

[borjaruiz]

Version 2.0.2

java.lang.IllegalArgumentException: Cannot add a null child view to a ViewGroup
at android.view.ViewGroup.addView(ViewGroup.java:4952)
at android.view.ViewGroup.addView(ViewGroup.java:4917)
at com.takusemba.spotlight.SpotlightView.startTarget(SpotlightView.kt:116)
at com.takusemba.spotlight.Spotlight.showTarget(Spotlight.kt:96)

Tried many things without success. I'm using java and in a Fragment
myView is found using Butterknife, and if I put a breakpoint before starting spotlight, it's not null

private List getTargets() {
List targets = new ArrayList<>();
targets.add(new Target.Builder().setAnchor(myView).setShape(new Circle(100f)).build());
return targets;
}

@OverRide
public void onViewCreated(View view, @nullable Bundle savedInstanceState) {
super.onViewCreated(view, savedInstanceState);
new Spotlight.Builder(getActivity()).setTargets(getTargets()).build().start;
}

[borjaruiz]

I just saw that if I put a .setOverlay(layout) it works fine.
I don't understand why it's mandatory to use a layout, furthermore it would be great to return a clearer exception message