title: Mime::Type::InvalidMimeType ("charset=utf-8" is not a valid MIME type)
body: <p>Since upgrading to Rails 6 we began getting these errors: <code>Mime::Type::InvalidMimeType ("charset=utf-8" is not a valid MIME type)</code>. I assume <code>charset=utf-8</code> doesn't make any sense as a MIME type, but can't rescue these errors out:</p>
  
  <pre><code>  rescue_from Mime::Type::InvalidMimeType, with: :raise_not_found
  </code></pre>
  
  <p>Is it possible this exception raises before even hitting our controller?</p>