When I click on categories in BO K2 menu then I get many lines with similar errors:

Notice: Trying to get property of non-object in ......../administrator/components/com_k2/views/categories/view.html.php on line 78

I check all permission on files and reinstall K2 component, I search on google and forums but sims no one had problems like this.

Any advice where to look for solution.

Thank you.

David

Hello David,

This is a notice and not an actual error, it will not affect your site's functionality in any way.
Try setting error reporting to none or system default when you have finished development.