[ENG-3637] Updating an existing Collection results in a 502

[Johnetordoff]

Purpose

Fix collections to allow updating via admin app.

Changes

• makes null study design/school data [''] a null JSON value.

QA Notes

Please make verification statements inspired by your code and what your code touches.

• Verify
• Verify

What are the areas of risk?

Any concerns/considerations/questions that development raised?

Documentation

Side Effects

Ticket

https://openscience.atlassian.net/browse/ENG-3637