Problem adding List component

1

Hi!
I created a class that adds a list component in a certain moment. Something like this:

import fl.controls.*; 
...
var myList: List = new List();
...
addChild(myList)

but in the last line, i get a huge error. I realized the error message disappears and everything works well if i put the list component in the library. Is it really necessary??? Here’s the error message. Thank you all in advance :wink:

TypeError: Error #1009: No se puede acceder a una propiedad o a un método de una referencia a un objeto nulo.
    at fl.containers::BaseScrollPane/drawBackground()
    at fl.controls::List/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::BaseButton/draw()
    at fl.core::UIComponent/drawNow()
    at fl.controls::ScrollBar/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::BaseButton/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::LabelButton/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::BaseButton/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::BaseButton/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::BaseButton/draw()
    at fl.core::UIComponent/drawNow()
    at fl.controls::ScrollBar/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::BaseButton/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::LabelButton/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::BaseButton/draw()
    at fl.core::UIComponent/callLaterDispatcher()
TypeError: Error #2007: El valor del parĂ¡metro child debe ser distinto de null.
    at flash.display::DisplayObjectContainer/addChildAt()
    at fl.controls::BaseButton/drawBackground()
    at fl.controls::BaseButton/draw()
    at fl.core::UIComponent/callLaterDispatcher()