Navbar stopped showing

[laggron42]

Hi, it seems the PR #162 stopped our navbar from showing at all, it was working perfectly fine before.

[cobaltt7]

I also had this issue and investigated:
https://github.com/fastapi-admin/fastapi-admin/blob/95b1c2e2f6c3263a31c82a2be622161b024be450/fastapi_admin/templates/layout.html#L18L23
<button> is missing a closing tag. The HTML parser ends up putting the entire navbar inside the button. The button is hidden on large screens entirely, causing the navbar to be hidden as well.