After updating our website to joomla 3.6, we are getting a fatal error when adding new K2 items from the frontend: Fatal error: Call to a member function isCheckedOut() on null in /administrator/components/com_k2/views/item/view.html.php on line 100 and a blank screen.

We currently have K2 version 2.6.9. How to correct this issue?

Hello,

You need to update K2 to its latest version or even better install the latest DEV version github.com/getk2/k2.

Hello Krikor,

I have the same issue with version 2.6.9, but I can't update to 2.7 because of several 3rd-party-plugins which do not run under 2.7. (I tested it ;)).
Do you have any other ideas to get editing on frontend to work again?

Thanks,
Matthew

This the file that will produce any error.

github.com/getk2/k2/blob/master/components/com_k2/views/item/view.html.php

You can Frankenstein it (backup first) but I do not know if other issues will arise.

"Frankenstein" :D
Currently I'm doing a backup of the site and try installing 2.7.1. If that doesn't work I'll try your suggested method. :)
Thanks... again...

Matthew.

You 're welcome :)

Report after updating to dev-build 2.7.1:
In the backend the tabs don't work anymore. All tabs (the links) and the content is above each other, console gives no JS-errors, all caches cleared, 3 different browsers tested.
And when editing in the frontend: the editor now shows up, but I can't save or close anything. The buttons for "featured" and "enabled" also don't work. Console gives following error in k2.js:
Got an advice before I need to roll back and Frankensteinin' it?

The entire UI (thus the markup) has been changed.
This means you need to clear both Joomla!'s and your browser's cache.
You were correct to do this. If you are using an obsolete override of itemform.php you might need to update it, although this is unlikely.

Can you check if jQuery is being loaded and if not, can you enable jQuery loading from K2's settings.

Update:
I updated jquery to version 2.1.3. The frontend JS error is gone. But there are still the tabs in front- and backend that don't work. :(

You were right: It was caused by my override of the itemform.php. I'll update it.

Summary: update jquery, update itemform.php

My problems: SOLVED --- Thank you so much, Krikor!!!


Btw.: What about my other templates? Do I have to update them, too?