[Lens] Clicking on the current field in Select a field in dimension editor throws an error

[mbondyra]

Steps to reproduce:

1. Open dimension editor in lens.
2. Select a field.
3. Once the field get updated, click the same field from the combo box.
4. You can close the whole flyout by clicking, but there's no way to close the combo box. Clicking on 'close' on the bottom of the flyout creates a view like the second screenshot

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)