Visual Metrics Editor doesn't let you cancel out of changes

[jkhwu]

Describe the bug
Visual Metrics Editor no longer allows canceling out of changes in the side panel

To Reproduce
Steps to reproduce the behavior:

1. Go to visual metrics editor in Rill Developer
2. Click on any measure/dimension and change stuff in the side panel
3. Click Cancel at the bottom of the panel
4. See warning dialog and click close

Expected behavior
Expect the right panel to close without making the changes; instead it just takes you back to the panel.

Screenshots

Desktop (please complete the following information):

• OS: iOX
• Browser: Chrome
• Version v58.1

Additional context
Not sure if this is a regression or has been implemented this way since the beginning