fix the generation of Function constructor argument

[siosonel]

Description

Fixes the issues as reported by Xiaotu.

@xzhou82 the blank values for microexpression and MAF columns are also blank in ppr, so I think my fixes address the missing data values.

Checklist

Check each task that has been performed or verified to be not applicable.

• [x] Tests: added and/or passed unit and integration tests, or N/A
• [x] Todos: commented or documented, or N/A
• [x] Notable Changes: updated release.txt, prefixed a commit message with "fix:" or "feat:", added to an internal tracking document, or N/A