Enable eval only when the samples directory is set

- when returning if the eval is enabled
- check if we have a proper sample directory
- maybe check if it is not empty
- return the result based on this

No files, tests, or entry points are named. Locate the code that reports whether evaluation is enabled, then inspect how the samples directory is configured and validated; done means evaluation is disabled when the directory is missing or empty and enabled only for a proper samples directory.

Written by the indexing model from the issue text.