PHP Notice when the admin options page slug is similar to the Freemius menu slug

[bfintal]

🐞 bug report

Behavior:

• What is the issue? (*) I have this in my SDK integration (retained only the relevant part):

$sugb_fs = fs_dynamic_init( array(
	// ...
	'menu' => array(
		'slug' => 'stackable',
		// ...
	),
) );

I also add my own menu page (intended to display some plugin options) where that slug starts with the same slug as the menu slug above:

add_action( 'admin_menu', function() {
	add_menu_page(
		__( 'Title', 'default' ), // Title of Page
		__( 'Menu', 'default' ), // Menu Title
		'edit_posts', // Permissions
		'stackable-test', // Slug
		'__return_false', // Callback Function
	);
} );

When logged in as a user without manage_options privileges, navigating to that menu page http://local.local/wp-admin/admin.php?page=stackable-test throws PHP notices:

Notice: Trying to access array offset on value of type bool in /.../plugin/freemius/includes/managers/class-fs-admin-menu-manager.php on line 710

Changing the admin page slug so as not to start with the Freemius slug fixes the issue.

• What is the expected behavior?

No PHP notice

Versions: (*)

• Freemius SDK Version: 2.4.2
• WordPress Version: 5.8
• PHP Version: 7.3

Plugin / Theme: (*)

• Name: Stackable
• Slug: stackable-ultimate-gutenberg-blocks
• Freemius ID: 1748