AttendeesChat.js

...

class AttendeesChat extends Component {
    ...

    render() {
        const { toggleAttendeesChat } = this.props;
        const { channel, unmount } = this.state;
        if (!channel || unmount) {
            return null;
        }
        return (
            <Portal>
                <Root style={this.rootStyle}>
                    <Chat client={this.chatClient} theme='messaging dark'>
                        <Channel channel={channel}>
                            <Window hideOnThread>
                                <ChatHeader onClose={toggleAttendeesChat} />
                                <MessageList />
                                <MessageInput />
                            </Window>
                        </Channel>
                    </Chat>
                </Root>
            </Portal>
        );
    }
}

...