Error flash output TypeError 1009:Cannot access a property or method of a null object reference

Question

Why I get output

TypeError: Error #1009: Cannot access a property or method of a null object reference.

at Untitled_1_fla::MainTimeline/asd()

this my code

stage.addEventListener(Event.ENTER_FRAME,asd)
function asd(e:Event){
    if(test.pemukul.hitTestObject(musuh)){
        musuh.visible=false
    }
}

Answer 1

some object you trying to access is null so check this objects:

test
pemukul
musuh