Describe the bug
Running Converse in fullscreen mode with a screen width between 576 - 768 px (I believe this is the sm media breakpoint) results in the controlbox being the only visible component with no way to view chats. Clicking on groupchats or contact chats does not open the chat view.

To Reproduce
Steps to reproduce the behavior:

1. Host the Converse development server with view_mode: 'fullscreen' set in the initialization of dev.html.
2. Open Converse in a browser and log in.
3. Resize the browser window to anywhere between 576 and 768 pixels.
4. The control box will be the only visible component.
5. Clicking on group or contact chats will not change the view.

Expected behavior
Clicking on a groupchat or contact chat should open the chat view for the chat and hide the control box or the control box should be open next to the chat view when the browser window is between 576 and 768 pixels.

Screenshots
Showing the chat view right before the breakpoint:

After bumping the width up 1px the ControlBox takes over and clicking on the chats will not open the chat view:

Moving the width up to 768px triggers the md breakpoint and the control box is open next to the chat:

Environment (please complete the following information):

• Desktop
• Browser: Chrome and Firefox
• Converse.js version 11

Additional context
I'm running a local OpenFire XMPP so my full initialize block in dev.html is:

{
    i18n: 'en',
    theme: 'nordic',
    dark_theme: 'dracula',
    auto_away: 300,
    loglevel: 'debug',
    show_background: true,
    message_archiving: 'always',
    muc_show_logs_before_join: true,
    whitelisted_plugins: ['converse-debug'],
    view_mode: 'fullscreen',
    show_controlbox_by_default: true,
    websocket_url: '{wss for my OpenFire}',
    auto_login: true,
    authentication: 'login',
    jid: '{OpenFire user}',
    password: '{password}',
    discover_connection_methods: false,
    muc_history_max_stanzas: 50
}

Just in case some other setting I'm using might be causing a conflict. Otherwise I'm running from a clean checkout from GitHub.