Undefined index: hook_suffix notice on wp_ajax_get_comments

[c3mdigital]

This is part 1 of a two part bug on displaying comments on post.php

The undifined index notice in the ajax response causes the error "an unidentified error has occurred" in the Comments post meta box.

( ! ) Notice: Undefined index: hook_suffix in /Users/chris/Sites/wp-trunk/wp-admin/includes/screen.php on line 401
Call Stack
#	Time	Memory	Function	Location
1	0.0004	254360	{main}( )	../admin-ajax.php:0
2	0.2893	18405672	do_action( )	../admin-ajax.php:69
3	0.2894	18407160	call_user_func_array ( )	../plugin.php:406
4	0.2894	18407192	wp_ajax_get_comments( )	../plugin.php:406
5	0.2895	18408880	_get_list_table( )	../ajax-actions.php:682
6	0.2920	18603376	WP_Comments_List_Table->__construct( )	../list-table.php:49
7	0.2921	18604688	WP_List_Table->__construct( )	../class-wp-comments-list-table.php:36
8	0.2921	18605480	convert_to_screen( )	../class-wp-list-table.php:88
9	0.2921	18605480	WP_Screen::get( )	../template.php:1873

Calling global $hook_suffix; in WP_Screen::get(); fixes the notice.

Related #21101

Confirmed.

Caused by [21914].

In [22085]:

Handle screen arg in WP_Comments_List_Table constructor. Avoids warning when calling WP_Screen::get() later. fixes #22039