Nested Instance Tables: Form save in popup fails if launched from popup

https://redcap.vumc.org/community/post.php?id=283416&comment=283753

If an instance is launched within the instance popup from another repeating form within the popup, rather than from a regular form page, the save will fail because this JavaScript error is thrown:

<img width="856" height="436" alt="Image" src="https://github.com/user-attachments/assets/ae5ed6f2-9669-42ae-8fd0-ec9a2738cf06" />