Remove child = null before setting it to null?

1

sometimes I remove child and trace it afterwards and it outputs null although I havent yet set it to null, why is that?
and do I need to set it to null also in that case?

trace(holderArr[loadedThumbs].getChildByName("photo_bg"));
//[object MovieClip]
holderArr[loadedThumbs].removeChild(holderArr[loadedThumbs].getChildByName("photo_bg"));
trace(holderArr[loadedThumbs].getChildByName("photo_bg"));
//null
holderArr[loadedThumbs].photo_bg = null;
//trace(holderArr[loadedThumbs].getChildByName("photo_bg"));
//null