[instrument_manager] 500 error even though file written to instrument directories

[zaliqarosli]

Describe the bug
500 error when uploading a valid file, no front-end error shows, but file gets written to project/instruments and sql file to tables_sql anyways

To Reproduce
Steps to reproduce the behavior (attach screenshots if applicable):

1. Go to '...'
2. Click on '....'
3. Scroll down to '....'
4. See error

What did you expect to happen?
A clear and concise description of what you expected to happen.

Browser Environment (please complete the following information):

• OS: [e.g. Plan9, HURD, Oberon, etc]
• Browser [e.g. chrome, firefox] (note that only these two browsers are supported)
• Version [e.g. 22]

Server Environment (if known):
Note: We only support the most recent release of LORIS.

• LORIS Version: [e.g. 22.0.0]
• Linux distribution and Version: [e.g. Ubuntu 16.04, CentOS 7]
• MySQL/MariaDB Version: [e.g. MySQL 5.7, MariaDB 10.3]

Additional context
Add any other context about the problem here.