Cannot edit the client fields of an event to be include more than 1 person

[ncduy0303]

Steps to produce:

• Use the default sample data
• Runs edit 2 n/Meetup s/01-12-2023 2pm e/01-12-2023 3pm c/Alex Yeoh c/Bernice Yu (this command was taken from the User Guide)

Outcome:

Problem: It is expected to be able to edit the selected events to have multple clients as mentioned in the User Guide, but an error (Multiple values specified for the following single-valued field(s): c/) was raised instead.