Issue Summary

Using the web version, in a Workspace Table View with cards showing members, if you try to remove a user, you'll get an error

"We couldn't add you to the card / Wait a moment then try it again"

In the console you can see the error "POST https://trello.com/1/cards/__________/idMembers 400 (Bad Request)"

This works correctly in the Trello app. The problem appears to be only on the web version.

Steps to Reproduce

1. In a browser, access Trello
2. Access a Workspace Table View
3. You need to have cards with the members showing on it
4. Try to remove one of the members from the card through the Workspace Table View. You'll get an error, and the user won't be removed. 

Expected Results

Remove the user

Actual Results

"We couldn't add you to the card / Wait a moment then try it again"

"POST https://trello.com/1/cards/__________/idMembers 400 (Bad Request)"

Workaround

Access the card and remove it directly on the board or use the Trello App.