NStep Workflow: error while validating a distinct Nstpe workflow on a two lang web site whose main page is not translated nor published

I have a Cropv2 site in two lang (FR and EN). The I create a page in FR only. I switch in english and I create a main_content object (in two lang) with a distinct Nstep workflow (Admin+Users groups on all steps).

Then, from the EN lang (no title on the page), I directly click on the main_content distinct worklow. This opens the Nstep workflow. I try to validate the FR lang from the EN page. This fires the followeing exception in the console:

2007-10-10 15:45:49,688: INFO [org.jahia.bin.Jahia] - Processed [/jahia/Jahia/engineName/workflow/site/test/op/edit/pid/49] user=[root] ip=[127.0.0.1] in [78ms]
2007-10-10 15:45:49,735: INFO [org.jahia.services.scheduler.BackgroundJob] - execute Background job BackgroundJob-efc852d9-c8d0-4982-a3f6-bb5ba654ad76
started @ Wed Oct 10 15:45:49 CEST 2007
2007-10-10 15:45:49,845: WARN [org.jahia.workflow.nstep.NStepWorkflow] - Error during workflow of object ContentContainer_262 in language en with process Three Validation Step Workflow
java.lang.NullPointerException
at org.jahia.services.containers.ContentContainer.getDisplayName(ContentContainer.java:333)
at org.jahia.workflow.nstep.NStepWorkflow.addActionToMailQueue(NStepWorkflow.java:1095)
at org.jahia.workflow.nstep.NStepWorkflow.sendAction(NStepWorkflow.java:683)
at org.jahia.services.workflow.ActivationJob.processWorkflow(ActivationJob.java:260)
at org.jahia.services.workflow.ActivationJob.executeJahiaJob(ActivationJob.java:107)
at org.jahia.services.scheduler.BackgroundJob.execute(BackgroundJob.java:133)
at org.quartz.core.JobRunShell.run(JobRunShell.java:195)
at org.quartz.simpl.SimpleThreadPool$WorkerThread.run(SimpleThreadPool.java:520)
2007-10-10 15:45:49,845: INFO [org.jahia.services.scheduler.BackgroundJob] - Background job (of type workflow) ended with status successful executed in 0s