Fix incorrect handling of the ROOT setting in configuration

[nicoyou]

This pull request fixes an issue where the ROOT setting was not being properly read from the configuration.
Due to this, the behavior relying on ROOT did not function as expected in some environments.

Changes made:
Ensured that the ROOT setting is retrieved correctly using getattr with a proper fallback.

Please let me know if any additional changes are needed. Thank you for maintaining this project.

[jrief]

Which issue does this solve?
Can I reproduce the problems in that issue?

[nicoyou]

@jrief
For example, when SASS_PROCESSOR_ENABLED is set to true in django 5.0 (4.2>=),
STORAGES['sass_processor'] = {
'BACKEND': 'django.core.files.storage.FileSystemStorage',
'ROOT': 'static path'
}
Even if you register a setting like this, ROOT will be ignored and the compiled css will be generated directly under the project or in the ROOT of FileSystemStorage.
This update will fix this issue.

[nicoyou]

@jrief
I don't have permission to merge into the master branch, so if you accept this pull request, please merge it.

[jrief]

Again: There is no issue with a description on how to rereduce this bus.

[nicoyou]

@jrief
I was mistaken, the issue in question is here.
But I couldn't link it.
#181