Make video stop video when leaving a frame = problem as not all frames have this video

Question

I know how to make a video (instanced as showreel) stop when clicking on a button that that navigates to another section/frame, since otherwise I would still listen to that video while not visible. The problem is when I'm in another frame that doesn't have that video, when clicking on the menu to go to whichever other frame, it looks for that it to stop if it's playing and it and doesn't find it, and so there's an error.
How can solve this? Maybe I should put an order saying something like if there exists a video in that frame instanced as sowreel, stop it, otherwise don't do anything as there is nothing to be stopped. Or assign the order to the frame (which is called motion), but I don't know how to do that, can someone help? The code I have is:
import fl.video.VideoEvent;
function onClick(evt:MouseEvent):void {
    if( showreel.playing ){
        showreel.stop();}
    gotoAndStop(evt.currentTarget.name);
motion.addEventListener(MouseEvent.CLICK, onClick);
web.addEventListener(MouseEvent.CLICK, onClick);
logo.addEventListener(MouseEvent.CLICK, onClick);
photo.addEventListener(MouseEvent.CLICK, onClick);

Answer 1

all assets, as far as possible, should be removed from the display list and readied for gc when no longer in use.  that includes flvplayback instances.
and yes, when you return to a frame or situation where you create an flvplayback instance, it will be created.  the removedfromstage event doesn't do anything except detect when something is removed from the stage:
flv.addEventListener(Event.REMOVED_FROM_STAGE,f);
function f(e:Event){
flv.stop();
that's it.
for a typical beginner to intermediate coder, flv will be on one frame of the main timeline.   adding those lines of code will ensure that when you move from a frame that contains flv (and that code), any video playing in flv will be stopped so you won't hear it when you navigate to another frame.