Admin CPT comments error

[dgwyer]

I'm seeing errors on the 'Dashboard', and 'Comments' admin pages when a CPT that supports comments has been deactivated (e.g. via a Plugin).

Reported error messages are:

Notice: Trying to get property of non-object in C:\wamp\www\wp\wp-includes\capabilities.php on line 1154
Notice: Trying to get property of non-object in C:\wamp\www\wp\wp-includes\capabilities.php on line 1155

Here is an example Plugin with steps to replicate the issue:

1. Activate Plugin (below) to enable the CPT.
2. Create a new 'Testimonial' and publish it to be able to leave a comment directly on the post edit screen.
3. View the comment on 'Dashboard' and 'Comments' admin pages (no visible errors).
4. Deactivate the Plugin and view 'Dashboard' and 'Comments' admin pages again. Errors are visible this time.

<?php
/*
Plugin Name: CPT comments error example
*/
function reg_cpt() {
		$args = array(
			'public' => true,
			'supports' => array( 'title', 'comments' ),
			'labels' => array( 'name' => 'Testimonials' )
		);
		register_post_type( 'tml', $args );
}
add_action( 'init', 'reg_cpt' );

[SergeyBiryukov]

Duplicate of #16956.

[dgwyer]

Why has status been set to closed, and milestone to not awaiting review?

*Update* Didn't see duplicate notice.