Getting Error #1009 with CellRenderers

I've been getting...

User exception thrown: TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at fl.controls::CheckBox/drawLayout()
    at fl.controls::LabelButton/draw()
    at fl.core::UIComponent/drawNow()
    at fl.controls::List/drawList开发者_运维技巧()
    at fl.controls::List/draw()
    at fl.core::UIComponent/drawNow()

for any CellRenderer that I'm using in the List. I've added all related components to my FLA directly, but am still getting the problem.

I figured out this after too many hours of debugging...

I had my CellRenderer class as an internal class alongside my public list based component. Once the CellRenderer based class was moved into its own AS file and made public then the error went away.

Now this solution is officially documented :)