Notifications: Hide "Details" button if there are none

Reason for the change

Makes for a cleaner look of simple jobs.

Test plan

• Checking and unchecking the button still works
• Button isn’t shown when there are no details, still shows when there are
• Button hides/shows properly when details come and go during the job’s lifetime (unlikely)
• Details collapse correctly when they go away

Screenshots or screen recordings

Before	After