Listener events field no longer shows a loading animation when retrieving events list

Summary

When you first open a listener configuration screen after a Jira restart we load the list of events a user can choose.
When loading this list, the events selection field should show a loading animation. This no longer displays in 6.13.0

Steps to reproduce:

1. Startup Jira and install scriptrunner 6.13.0
2. Go to the listener's page and create a new listener

Expected result

The events field shows a loading animation when getting the list of events

Actual result

The events field is selectable and shows no options when clicked, however, if you wait around minute it will load the events