form_alter using array as array key causes php warning.

ctools/plugins/content_types/views_row.inc

'edit form' => array(
  'views_content_views_row_content_type_edit_form' => t('Select context'),
  'views_content_views_row_edit' => t('Configure rows'),
),

I haven't figured why yet, but the above array ends up as $form_id in

function _semantic_panels_rewrite_push_form_alter($form_id) {
  $cache = &drupal_static(__FUNCTION__, array());

  if ($form_id !== NULL && !isset($cache[$form_id])) {
    $cache[$form_id] = $form_id;
  }

  return $cache;
}

Meaning an array is used as an array key, causing a nasty looking error message.