Wpuf upload and loop_shop_per_page conflict

Hi there is a conflict in my site’s frontend.

In functions.php there is code like this:
add_filter( 'loop_shop_per_page', create_function( '$cols', 'return 12;' ), 20 );

I arrange product numbers per page by this.Whenever I remove it wpuf can not upload images.Even if I change $cols with number it gives error 200.Now it is working but it is interesting for me.Why it happens?