I've already checked in the code change to our repository/issue tracker, so it will be in the next releases going forward. I would recommend doing it on your other sites, especially if they're running the newer PHP version too.
It's a small nuance of one of the PHP methods we're using. In /libraries/sourcecoast/openGraphPlugin.php, around lines 345-348, there is code to grab the text of an article, split by whitespace and then get the appropriate number of words to build the og:description.
if (function_exists('mb_split'))
$parts = mb_split('\s+', $articleText);
else
$parts = preg_split('\s+', $articleText);
was replaced with
if (function_exists('mb_split'))
$parts = mb_split('/\s+/', $articleText);
else
$parts = preg_split('/\s+/', $articleText);
The first code block was working prior to your upgrade, but the second block is better. I think earlier versions of PHP were more lenient, so when you upgraded the first block no longer works.
-Melissa