omega_html_head_alter() leads to invalid markup

Problem/Motivation

The implementation

/**
 * Implements hook_html_head_alter().
 */
function omega_html_head_alter(&$head) {
  // Simplify the meta tag for character encoding.
  $head['system_meta_content_type']['#attributes'] = array(
    'charset' => str_replace('text/html; charset=', '', $head['system_meta_content_type']['#attributes']['content']),
  );
}

in combination with the default html.tpl.php leads to invalid HTML markup if

if (omega_extension_enabled('compatibility') && omega_theme_get_setting('omega_conditional_classes_html', TRUE)):

in the template return true.

You can reproduce this when validating a site meeting the mentioned conditions with the W3C validator at http://validator.w3.org/check.

The validator will output the following message:

Proposed resolution

Add the opposite condition of the one in the template within omega_html_head_alter to prevent altering of the tag if conditional classes are added to the markup (which would push the tag out of the first 512 bytes).