Bug study bugs

[karimouf]

Description

• Fixed an issue where the generated study link contained undefined instead of the correct hash.
• Fixed an issue where newly created studies were missing the reference to the original study they were based on.

Bug Fixes

1. Corrected study link generation by ensuring a valid hash is created and assigned before building the URL.
2. Ensured that newly created studies properly store and maintain the reference to their parent/base study.