Undefined index: content in metatag_page_build()

I add this error after installing the module Meta Tags version

Notice : Undefined index: content in metatag_page_build() (ligne 651 dans /sitepath/sites/all/modules/metatags/metatag.module).
And all my admin page were un-accessible.

I just added a test, remplacing this line (l.651 in both -dev and -alpha1 metatag.module files):

  $page['content'] = array('metatags' => array()) + $page['content'];

By those :

  if (isset($page['content'])) $page['content'] = array('metatags' => array()) + $page['content'];
  else $page['content'] = array('metatags' => array());