Have Thumbnail Image set to No Image as default

I am also facing the same issue, while editing the node.Ideally it should work without selection of image as well.

I have this issue as well, and it seems to potentially be further complicated when I try to setup a default value of the OG Image as well.

It seems to me that setting a default value for og:image causes the problem.
Leaving it blank uses the "no image" option as default.

Details:
in opengraph_meta.module the thumbnail image options include a blank
'' => t('No image (Facebook will choose one automatically).')
the other options are "harvested" from the node. The selected default value is then set by

'#default_value' => $metatags['og:image']['value']['#default_value']

So if og:image is set but does not correspond to a node image, the select will be broken.

Additionally even if the default value is a node token, e.g. [field_image], during the select widget creation this value does not seem to be resolved to the corresponding url. So the select field will not have the correct option pre-selected.

As suspected the token is not replaced during the select widget creation. So to pass the default select field validation the token has to be added to the '#options' array.

I created a patch that does this, while not actually rendering the option as a selectable choice.

If you do not want to patch the module, you could probably use hook_form_alter to do the same.
Untested, but something similar to this should work.

function hook_form_FORM_ID_alter(&$form, $form_state, $form_id) {
  if(!array_key_exists('opengraph_meta', $form){
      return;
  }
  $default_value = $form['opengraph_meta']['image']['#default_value'];
  if(!isset($form['opengraph_meta']['image']['#options'][$default_value])) {
      //add default value, so validation passes
      $form['opengraph_meta']['image']['#options'][$default_value] = "Default";
      $form['#pre_render'][] = 'hook_form_remove_default';
  }
}
function hook_form_remove_default($element) {
  $image = &$element['opengraph_meta']['image'];
  unset($image['select'][$image['#default_value']]);
  return $element;
}

This is the same as #5 but with the paths tidied up so we can apply it against the module directly.

# 5 and and #6 both working for me. Thanks for patch.