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I was checking my Joomla error log and noticed that this error message is appearing nearly every second. I can see no adverse effects except that my log file is growing extremely large on a regular basis. Also, none of my other sites have JomSocial and this is the only site that is having this issue.
Error: PHP Notice: Undefined index: HTTP_HOST in /var/www/html/mysite.com/public_html/libraries/joomla/application/web.php on line 863
Note: I changed the domain name to "mysite.com" for privacy.