Follow-up to https://github.com/jenkinsci/jenkins/pull/4348 and JENKINS-60092. As proposed by jglick in https://github.com/jenkinsci/jenkins/pull/4348#issuecomment-554381425 , it would be great to return a default view in ViewGroupMixIn#getPrimaryView() so that the API users do not have to worry about edge cases when views are not defined.

IIRC I tried it also and hit some other obstacles, but I do not remember which ones. So there *might* be some obstacles like view persistence