Notice: Undefined index: translate en field_collection_field_formatter_settings_form()

This error appears when modifying a content type display which has a Field Collection, and you edit the formatter settings for a non translatable Field Collection.

Steps:

1. Create or edit a content type
2. Create a Field Collection field
3. Go to the content type "Manage display"
4. Click on the field collection field settings
5. Save the field collection field settings

The solution is just to test for the 'translate' index ($settings['translate'] ? $settings['translate'] : '') in field_collection_field_formatter_settings_form:

    $elements['translate'] = array(
      '#type' => 'textfield',
      '#title' => t('Translate link title'),
      '#default_value' => isset($settings['translate']) ? $settings['translate'] : '',
      '#description' => t('Leave the title empty, to hide the link.'),
      '#access' => field_collection_item_is_translatable(),
    );