Ensure module dependencies for value null, is an empty Set (#10877)

* ensure we have no dependencies when `absoluteFilePath` is `null`

This happens in the CLI where we don't have a guaranteed `path` for the
config file. This can happen in practice if you use:

```console
npx tailwindcss --content ./index.html -o ./output.css
```

... and if you don't have a `tailwind.config.{js,ts,cjs,...}` in the
current directory.

* update changelog

CHANGELOG.md

@@ -29,6 +29,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Disallow multiple selectors in arbitrary variants ([#10655](https://github.com/tailwindlabs/tailwindcss/pull/10655))
 - Sort class lists deterministically for Prettier plugin ([#10672](https://github.com/tailwindlabs/tailwindcss/pull/10672))
 - Ensure CLI builds have a non-zero exit code on failure ([#10703](https://github.com/tailwindlabs/tailwindcss/pull/10703))
+- Ensure module dependencies for value `null`, is an empty `Set` ([#10877](https://github.com/tailwindlabs/tailwindcss/pull/10877))
 
 ### Changed
 

src/lib/getModuleDependencies.js

@@ -72,6 +72,7 @@ function* _getModuleDependencies(filename, base, seen, ext = path.extname(filena
 }
 
 export default function getModuleDependencies(absoluteFilePath) {
+  if (absoluteFilePath === null) return new Set()
   return new Set(
     _getModuleDependencies(absoluteFilePath, path.dirname(absoluteFilePath), new Set())
   )