org-sidebar-tree 'wrong type argument: stringp, nil'

Hello,

I’m new to this package, so please be gentle! I’ve been trying to use the `org-sidebar-tree` functionality to help navigate large Org files, but I keep getting the error:

`wrong type argument: stringp, nil`
when running M-x org-sidebar-tree from an Org buffer.

To troubleshoot, I started fresh with a clean Spacemacs install, only adding the `org` and `org-sidebar` packages, but the error persists. All dependencies appear to be installed correctly.

I’m wondering if this is a known issue or if there’s something obvious I might be missing. Any guidance or pointers would be greatly appreciated!

Thank you!