fix: correctly trailing slash redirect when navigating from root page

[eltigerchino]

fixes #11317

#10763 introduces a bug where the trailing slash option at the root page is set to always. This PR checks if a base config is set before setting trailing slash to always for the root page.

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[benmccann]

thanks! I just tweaked a couple docs type stuff. looks good to me! really appreciate the fix - a lot of people have been hitting this!

[eltigerchino]

Thanks for fixing it up and reviewing this on a weekend!