Script registry throw stack trace in the browser console

Problem

Create a valid custom listener and an error throws in the browser console after run Script Registry. However, the Script Registry does not show any error message in the UI:

Steps to reproduce it

1. On the filesystem, create a $JIRA_HOME/scripts/testlistener.groovy file containing 'return "Hello";'
2. Go to Listeners, click 'Create Listener' and choose 'Custom Listener'.
3. Select All Projects (doesn't really matter), All Issue Events, and Script File 'testlistener.groovy'.
4. Click 'Update' to save the listener
5. Click the 'Built-in Scripts' tab, then 'Script registry'
6. Open the Network tab in your browser, and watch atlassian-jira.log
   
   
7. Click 'Run'. In amongst the 200 responses you'll see a 500 response, and a stacktrace.