Error after updating "Pipeline: Job" plugin

[CarlesCapdevila]

I had a correctly working Jenkins instance with Gitblit Organization plugin installed and Pipeline: Job 2.12.2. When I upgraded Pipeline: Job 2.12.2 to 2.15, the Jenkins instance showed some errors at restart, including in the UI.

Excerpt of the error: The organization job's config.xml could not be read: CannotResolveClassException: org.jenkinsci.plugins.workflow.multibranch.WorkflowMultiBranchProject

Steps to reproduce:
1.- Have an instance of Jenkins with Organization Plugin and Pipeline: Job 2.12 installed.
2.- Upgrade Pipeline: Job to 2.15
3.- Restart Jenkins

UPDATE: This may be caused by a change not yet introduced, the triggering of scanning new repositories via Gitblit push hook.