Cannot access a property or method of a null object reference

1

I get the error:

Cannot access a property or method of a null object reference.

when I uncomment
//targetArray.push(target2);

stop();
var targetArray:Array;
var target2:Target= new Target("eggs", 5);//:Target = new Target("ribbon", 9);
//targetArray.push(target2);

target2.x=90;
target2.y=90;
addChild(target2);

Can’t I create an array of instances?