joomla - k2 json output not as expected -

i have website in joomla using k2 , utelizing json output using ?format=json whitch has been working fine antil yesterday randomly giving me warning error on json output before json starts:

<br /><b>warning</b>:  creating default object empty value in <b>/var/www/example.com/components/com_k2/views/itemlist/view.json.php</b> on line <b>149</b><br /> 

i cant find thing have ideas.

in json.php line 149, need create object before assigning value

  //category k2 plugins   $category->event = new stdclass();   $category->event->k2categorydisplay = ''; 

this have been solve problem in the future release. fix on github