Deprecation warning in sidebar.scss

Problem/Motivation

I created based on this theme, my custom theme. While working on it, I encountered an error returned by the SCSS compiler:

Deprecation Warning on line 31, column 17 of ../../contrib/bootstrap_barrio/scss/components/sidebar.scss: 
This operation is parsed as:

    0 - ($spacer)

but you may have intended it to mean:

    0 (-($spacer))

Add a space after - to clarify that it's meant to be a binary operation, or wrap
it in parentheses to make it a unary operation. This will be an error in future
versions of Sass.

More info and automated migrator: https://sass-lang.com/d/strict-unary
   ╷
31 │         margin: 0 -($spacer);
   │                 ^^^^^^^^^^^^
   ╵

Proposed resolution

I created a patch to solve this problem.