Fix for video stories not playing

ts/components/StoryViewer.tsx

@@ -265,6 +265,10 @@ export const StoryViewer = ({
   // We need to be careful about this effect refreshing, it should only run
   // every time a story changes or its duration changes.
   useEffect(() => {
+    if (!storyDuration) {
+      return;
+    }
+
     strictAssert(
       progressBarRef.current != null,
       "progressBarRef can't be null"