Olivero sidebar region produces whitespace output that the page template considers is an existing sidebar

This is likely related to 🌱 [meta] Themes improperly check renderable arrays when determining visibility Needs work . I wonder if within region--sidebar.html.twig, if we change the {% if content %} to {% if content.0 %}, if that'd be a good enough fix. It seems to solve the problem on my local.

If we change {% if content %} to {% if content.0 %} then it doesn't display the aside region even if we add any block in aside region.

Also, I printed the length of content in sidebar having Book navigation menu, {{ content|length }} and the output is 215. It seems to be an issue with the block itself.

Maybe its the book navigation block only. It adds the olivero book library (got it, library, haha?!) even if there was no content in the block.