Use vh instead of % to fix storybook rendering of chat container.

web/components/chat/ChatContainer/ChatContainer.tsx

@@ -102,7 +102,7 @@ export default function ChatContainer(props: Props) {
     () => (
       <>
         <Virtuoso
-          style={{ height: 'calc(100% - 110px)', width: 'auto' }}
+          style={{ height: 'calc(100vh - 170px)', width: 'auto' }}
           ref={chatContainerRef}
           initialTopMostItemIndex={messages.length - 1} // Force alignment to bottom
           data={messages}

web/stories/ChatContainer.stories.tsx

@@ -35,8 +35,8 @@ const AddMessagesChatExample = args => {
       </button>
       <ChatContainer
         messages={chatMessages}
-        usernameToHighlight={null}
+        usernameToHighlight="testuser"
-        chatUserId={null}
+        chatUserId="testuser"
         isModerator={false}
         isMobile={false}
       />