Hello,
@Nirjonadda
We checked the compatability with the product mentioned, and there does not seem to be any problem. The error you are getting is from the product itself, in file /upload/library/TilkiBey/ThreadCount/Extends/DataWriter/Forum.php and is not connected with our product and you would get the same error deleting that thread using other methods as well.
The product, however, seems to be written properly, and it checks if the thread has a user ID assigned to it or no. The error would be possible only if thread table has a user ID in it, but the user is actually deleted. This should not happen if you have deleted the user manually but would happen if you have deleted the user manually from the database, or used some add-on, that did not update the thread to be associated with user ID 0 when it removes a user.
Thank you!