There is always an empty changeset in BlueOcean for the latest run of a project when navigating to BlueOcean from the classic UI for that run (from https://<jenkins-server>/job/<project>/<runId>, click the Open Blue Ocean link in the left hand side navigation bar).

This issue occurs for standard pipeline jobs using checkout steps with the perforce scm configured (p4-plugin). The pipelines are defined using scripted pipeline. The issue is not likely limited to this context.