Handle edge cases in filtering

**Problem**
When working with helpers, the error messages could be more descriptive.

**Suggestion**
Improve error handling and add detailed error messages.

**Context**
This would help with debugging and maintenance.

The issue names no files, tests, or entry points. Start by locating the helper filtering code and its current error paths; done means the relevant edge cases are defined and detailed error messages are covered by tests.

Written by the indexing model from the issue text.