Have you tried disabling the "Open Graph - Content" plugin and just leaving the "Open Graph - JReviews" plugin enabled? If you don't have any normal Joomla content on the page and just have JReviews listings, then a quick fix would be to disable the "Open Graph - Content" plugin.
However, If you need to keep the plugin enabled, you could make a small code change to see if it helps.
In /plugins/opengraph/content/content.php at line 322, try replacing:
if(get_class($article) == 'JTableContent')
with
if(!is_array($article) && get_class($article) == 'JTableContent')
I can't reproduce the error you're having on my test site with JReviews, so that code snippet is untested. What version of JReviews are you using?
-Melissa