removeChild problem

1

I thought I had got the hang of this but no…

package {

    import flash.display.*;
    import flash.events.*;    
    import flash.net.*;
    import flash.text.*;    
        
    public class Test extends Sprite {            
    
    private var _diffClass:aDifferentClass;
    
        public function Test() 
        {
            innit();                        
            stage.addEventListener(MouseEvent.CLICK, changeSomething);
        }    
        private function innit():void
        {
            var _diffClass= new aDifferentClass();
            _diffClass.x = 0;
            _diffClass.y = 0;        
            addChild(_diffClass);

        }                
        private function changeSomething(e:Event):void
        {
            removeChild(_diffClass);
            innit();            
        }
    }
}

I want it so that when the stage is clicked, the _diffClass child which has been added already is deleted and then added again (with different values, but i havent added all that as to make this example simplier). I get the error: Error #2007: Parameter child must be non-null.
thanks
dai