Hello, this 2 notices in error log appears approximately every 30 seconds, sometimes every 1-3 minutes. (probably every single pageview, including bots views) That is my only error in log file. What could be the problem?

[Tue Dec 1 16:17:28 2015] [ow_core_log] [Notice] Message: Undefined index: nocontent File: /home/userxyz/web/mydomain.XYZ/public_html/ow_smarty/template_c/b8739aa1fd42aa3b7fd93785eec13a3ef6626d98.file.item_user_widget.html.php Line:57

[Tue Dec 1 16:17:28 2015] [ow_core_log] [Notice] Message: Trying to get property of non-object File: /home/userxyz/web/mydomain.XYZ/public_html/ow_smarty/template_c/b8739aa1fd42aa3b7fd93785eec13a3ef6626d98.file.item_user_widget.html.php Line:57