My b2evolution Version: 1.9.x

I am getting an error exact notice is said:

Notice: Only variable references should be returned by reference in
/inc/MODEL/files/_filelist.class.php on line 846

Searching this forum I've found a post but that post is locked item.

Others are talking about;
inc/MODEL/dataobjects/_dataobjectcache.class.php
That issue was also for me and it was solved.

Then there are no conversation for;
/inc/MODEL/files/_filelist.class.php on line 846

I could upload the file, function seems alright but error message is still there.

Thanks for your help, in advance,