Clean up HLS stream

Without this, it will continue loading chunks in the background.

layers/dot-cams/index.js

@@ -62,6 +62,7 @@ for (let [state, url] of Object.entries(allStates)) {
                 var hls = new Hls();
                 hls.loadSource(view.src);
                 hls.attachMedia(video);
+                vectorLayer.destroyPopupCallback = () => hls.destroy();
             }
             // iDevice support, untested (only works in Safari; required for iPhones)
             else if (video.canPlayType('application/vnd.apple.mpegurl')) {