Wordpress - category__in is not listing on $wp_query with SEO urls
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Hello I have a very simple plugin 

    add_action('pre_get_posts', 'post_page');

    function post_page()
    {
    
     global $wp_query;		
     if(is_category())
     {
    	echo '<pre>';
    	print_r($wp_query);
    	exit;
     }
     
    }

I have to get the category ids with in my plugin, I am getting without SEO urls but category__in is empty with SEO urls 

see without SEO friendly url : http://phpxpert.com/?cat=3 (category__in not emtpy)

with seo friendly url : http://phpxpert.com/category/jquery/ category__in  is emtpy

why this is happening and how can I get post_id and category_ids in my plugin

thank you 