Notice thrown on recent comment widget for comments on custom post type

[firebird75]

If a plugin creates a custom post type and some comments are posted for the custom post, then once the plugin is deactivated, this will generate a lot of notices in the recent comments widget on the dashboard :
"Notice: Trying to get property of non-object in /homepages/wp-includes/capabilities.php on line 1123

Notice: Trying to get property of non-object in /homepages/wp-includes/capabilities.php on line 1124

Notice: Trying to get property of non-object in /homepages/wp-includes/capabilities.php on line 1124

Notice: Trying to get property of non-object in /homepages/wp-includes/capabilities.php on line 1127

Notice: Trying to get property of non-object in /homepages/wp-includes/capabilities.php on line 1127"

Some robustness is required there :

		if ( ! $post_type->map_meta_cap ) {
			$caps[] = $post_type->cap->$cap;
			// Prior to 3.1 we would re-call map_meta_cap here.
			if ( 'read_post' == $cap )
				$cap = $post_type->cap->$cap;
			break;
		}

                $status_obj = get_post_status_object( $post->post_status );
		if ( $status_obj->public ) {
			$caps[] = $post_type->cap->read;
			break;
		}

Suggested fix :

		if ( is_object($post_type) && ! $post_type->map_meta_cap ) {
			$caps[] = $post_type->cap->$cap;
			// Prior to 3.1 we would re-call map_meta_cap here.
			if ( 'read_post' == $cap )
				$cap = $post_type->cap->$cap;
			break;
		}

		$status_obj = get_post_status_object( $post->post_status );
		if ( $status_obj->public ) {
			if (is_object($post_type))
			$caps[] = $post_type->cap->read;
			break;
		}

Same on line 1181 :

case 'edit_comment':
		$comment = get_comment( $args[0] );
		$post = get_post( $comment->comment_post_ID );
		$post_type_object = get_post_type_object( $post->post_type );
		if (is_object($post_type_object)) // Test added here
		$caps = map_meta_cap( $post_type_object->cap->edit_post, $user_id, $post->ID );
		break;

[SergeyBiryukov]

Duplicate of #16956.

[ddavout]

The fix is not a duplicate and seems easier to apply than the patch proposed 2 years ago in #16956.
Thanks to firebird75 ...

[SergeyBiryukov]

The ticket reports the same issue, so it's a duplicate.

The patch in #16956 was actually proposed 8 months ago.