Main Menu in collapsible region not visible

im getting this too but its a bit strange, ive made two themes from the same subtheme code on two different sites, one site the collapsible works and the other nothing shows on the page at all or in the markup if its placed in collapsible.

EDIT.........................
Figured it out... To reproduce.
go to /admin/structure/block
remove all the blocks from Navigation section...
place some blocks into the Collapsible section...

Since they're tied together in page.html.twig if nothing is in the Navigation section the collapsible wont show either.

Fix
Just change lin 66 on page.html.twig to
{% if page.navigation or page.navigation_collapsible %}

No patch.

sorry :0
seemed too tiny for a patch, but yea its always better with a patch.

Thanks for the patch.

Cheers for the awesome theme man, ive switched mine to sass and grunt but its essentially the same, such a good starting point for d8 & really flexible. Thanks for putting it out for everyone.