Agreed about Johnstone being nervy.
Also think it's about mentality. At 1-0 you've got to be hungry, crush them. You don't sit back at 1-0 when you're playing an inferior team.
I'd rather us not play HRK again, not even as a sub. No goal threat, we'd be better off giving 20mins to Zohore. Also, complete waste that Robinson was an unused sub.