BaseComponent.drawChildren() gets the current focus handler and checks if the highlight should be drawn. However, ParentComponent.focusHandler() allows nullable return value, so calling focusHandler.lastFocusSource() can cause a NullPointerException.

So uh, insert a if (focusHandler != null && ...)

While some extra assertions to clarify might certainly be of help, this is not a bug.

The only circumstance under which a component returns a null focus handler is when it's not correctly mounted - in which state it also does not support being drawn.

May I inquire how you discovered this? Likely your component was not mounted, but if we can rule that out there might be a different bug somewhere

Cheers

If this issue is still of concern, please reopen it - I'll go ahead and close it for now
Cheers