Handle edge cases in filtering

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

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

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

Start by locating the parser and filtering error-handling paths in the repository, then inspect how current errors are constructed. Identify the filtering edge cases covered by the issue and make the resulting messages more descriptive; done means those cases provide useful debugging context.

Written by the indexing model from the issue text.