Canceling edit breaks down adding new machines

Here's how to repro this problem:

1. start as usual (rake docker_up)
2. add machine (don't close the tab)
3. click the crayon icon near the agent-kea:8080, click cancel
4. try to add another machine

When I click on the add new machine, there's the popup (this works as intended). But once I type the name and click add, nothing happens visually and there's this error in the console.