[configuration] Error trying to remove field values

[zaliqarosli]

Describe the bug
The following error occurs when trying to remove values with the red x button for fields:

• excluded_series_description in Imaging Pipeline tab
• bids_dataset_authors and bids_validator_options_to_ignore in MINC to BIDS Converter Tool Options tab

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.