Hides pipeline duration in commit box when it is zero (nil)

What does this MR do?

Hides the duration info when the last pipeline has no duration.

Why was this MR needed?

@EvgenyOrekhov pointed in #32788 (closed) that GitLab was showing Pipeline ... running in 0 seconds.

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together

What are the relevant issue numbers?

Closes #32788 (closed).