You cannot clear the goal selection

This bug has appeared after the removal of extJS

Steps to reproduce:

1. Go to the HAP channel
2. Click on a component
3. Copy the variant
4. Select "Dutch" segment
5. Go to the Experiments tab
6. Select a goal for the experiment
7. Delete the goal

Expected result:

You can delete the goal

Actual result:

You cannot delete the goal.

This is useful if you want to restart/stop the experiment.