The setup of $variables['tags'] in template_preprocess_opengraph_filter() loops through the provided og tags ($variables['metatags']['og'][$key]). Later in the function, it sets up $theme_images (near line 425) by using title => $variables['tags']['title'] -- but there's no guarantee that the URL we've pulled in provides that metatag. As an example, I used http://facebook.com which seemingly does not provide the title.
The easiest thing is to perhaps suppress the PHP warnings by using @$theme_images = ... instead. Probably a better fix is something like:
title => (isset($variables['tags']['title']) ? $variables['tags']['title'] : '')
Identify the best solution. Implement it.
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Closed: duplicate
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