Gracefully close the story viewer when we cannot find story

Co-authored-by: Josh Perez <60019601+josh-signal@users.noreply.github.com>

ts/state/smart/StoryViewer.tsx

@@ -59,16 +59,6 @@ export function SmartStoryViewer(): JSX.Element | null {
 
   const getStoryById = useSelector(getStoryByIdSelector);
 
-  const storyInfo = getStoryById(
-    conversationSelector,
-    selectedStoryData.messageId
-  );
-  strictAssert(
-    storyInfo,
-    'StoryViewer: selected story does not exist in stories'
-  );
-  const { conversationStory, distributionList, storyView } = storyInfo;
-
   const recentEmojis = useRecentEmojis();
   const skinTone = useSelector<StateType, number>(getEmojiSkinTone);
   const replyState = useSelector(getStoryReplies);
@@ -81,6 +71,17 @@ export function SmartStoryViewer(): JSX.Element | null {
     getHasReadReceiptSetting
   );
 
+  const storyInfo = getStoryById(
+    conversationSelector,
+    selectedStoryData.messageId
+  );
+
+  if (!storyInfo) {
+    return null;
+  }
+
+  const { conversationStory, distributionList, storyView } = storyInfo;
+
   return (
     <StoryViewer
       currentIndex={selectedStoryData.currentIndex}