Reset workflow modal bugs

[varunbpatil]

Describe the bug
The "Reset Workflow" modal has a few small bugs.

1. Allows clicking "Confirm" without selecting an event-id which results in an error from the backend.
2. The error is not displayed to the user because the modal is closed immediately.
3. The description for the event-id radiogroup should be fixed in position instead of scrolling along with the event id's.

Expected behavior

1. "Confirm" button should be disabled if an event-id is not selected.
2. The modal should not be closed on an error.
3. The description for the event-id radiogroup should be fixed in position.