fix(FN-3843): fix record correction "bank commentary" being stored as an empty string

[sw-mattw]

Introduction ✏️

When 'Other' is not one of the record correction request reasons, the bank commentary field is optional.

The existing parsing trimmed any whitespace, but stored an empty string value if no input was provided (instead of undefined). This led to some other pages (e.g., "check the information" and the "record correction log") not rendering a hyphen when the bank commentary field was left blank (instead this rendered nothing which isn't consistent with our other tables).

Resolution ✔️

• Ensure that an empty "additional information" input value is stored as undefined
• Add additional tests

Screenshot showing the first row, which doesn't have 'Other' as a reason, rendering a hyphen ("-") in the "correction notes" column as the "additional information" input was left empty when this correction was submitted:

Miscellaneous ➕

N/A