Seek to correct location on close and reopen video

When closing and reopening a video, the video would start at the previous
progress point. Now it will correctly seek to the last progress point at close.

frontend/src/components/EmbeddableVideoPlayer.tsx

@@ -37,6 +37,13 @@ const EmbeddableVideoPlayer = ({ videoId }: EmbeddableVideoPlayerProps) => {
 
   const { data: videoResponseData } = videoResponse ?? {};
 
+  useEffect(() => {
+    if (!videoId) {
+      setVideoResponse(undefined);
+      setPlaylists(undefined);
+    }
+  }, [videoId]);
+
   useEffect(() => {
     (async () => {
       if (!videoId) {