Document type editor removes hippotranslation:translated mixin from prototype

• Create project from archetype, build and run as described on http://www.onehippo.org/7_8/trails/developer-trail/hippo-baby-steps.html.
• Log in to CMS console as admin.
• Check the node /hippo:namespaces/myhippoproject/newsdocument/hipposysedit:prototypes/hipposysedit:prototype, you will see it has the mixin hippotranslation:translated.
• Log in to CMS as admin.
• Go to documents tab, configuration section.
• Select hippo:namespaces/myhippoproject.
• Open newsdocument, click Edit.
• Click Done.
• Click Type actions -> Commit.
• Browse to Documents, myhippoproject/News/2011.
• Create a new newsdocument here.
• Edit the new newsdocument, enter some content, click Save & Close.
• Notice that the languages menu in the workflow bar is missing.

In the CMS Console, check the node /hippo:namespaces/myhippoproject/newsdocument/hipposysedit:prototypes/hipposysedit:prototype, you will see it has no mixin hippotranslation:translated.