Newbie: Cannot access a property or method of a null object reference help!

programming flash
1

So I’m trying to make a circle that moves left and right and creates a bullet that moves up. I have two classes, the circle and the bullet. When I try to run the code, I get: TypeError: Error #1009: Cannot access a property or method of a null object reference.
at Bullet/::enterFrameEvents()

here’s my code for the Bullet Class that is created:

package {
    
    import flash.display.*;
    
    import flash.events.*;
    
    import Character;
    
    public class Bullet extends MovieClip {
        private var bulletSpeed:Number = 10;
        
        
        public function Bullet(){
                addEventListener(Event.ADDED, beginClass);
                addEventListener(Event.ENTER_FRAME, enterFrameEvents);
        }
                
                private function beginClass(event:Event):void{
                    this.x = 200;
                    this.y = 30;
                }
                
                
                private function enterFrameEvents(event:Event):void{
                    this.y += bulletSpeed;
                    
                    if (this.y >= 400){
                        
                    this.parent.removeChild(this);

                    }
                }
                    }
    }

also, I know the bullet is always created in the same spot. I don’t know how to do that yet. Thanks