Workflow Panel displays error before starting a workflow for a terminal page

Steps to reproduce:

• have a non-terminal page with a work flow set up properly (i.e. it has a target page, maybe even already published)
• create a new terminal page as a subpage of that page
• type in some content and view the newly creates page

the panel creates an error message:

 Error invoking method 'get(java.lang.Integer)' in java.util.ArrayList at 952:xwiki:PublicationWorkflow.PublicationWorkflowPanel[line 73, column 71]
[...]
Caused by: java.lang.IndexOutOfBoundsException: Index: 4, Size: 4