Adding taggable mixin makes document type unusable

When the 'Taggable' mixin is added to a document type, existing documents of that type can no longer be viewed or edited in the CMS.

Steps to reproduce:
1. login to the archetype CMS as admin
2. edit the 'newsdocument' type
3. add the 'Taggable' mixin (from the 'Mixins' section on the right-hand side)
4. save & close the type and commit it
5. click on an existing news document

Expected: the news document is opened for viewing
Actual: an empty tab opens and the stacktrace below logged. It is no longer possible to view or edit existing news documents. Worse, when a news document was already opened for editing, the CMS will just show a blank page.

Stacktrace:

[INFO] [talledLocalContainer] 13.05.2014 12:45:33 ERROR http-bio-8080-exec-4 [MarkupContainer.renderNext:1435] Unable to find component with id 'mixins' in [MixinLoaderPlugin [Component id = item]]
[INFO] [talledLocalContainer] Expected: 'root:tabs:panel-container:cards:2:panel:center:tabs:panel-container:cards:1:panel:editor:extension.editor:template:view:6:item:mixins'.
[INFO] [talledLocalContainer] Found with similar names: 'root:tabs:panel-container:cards:2:panel:center:tabs:panel-container:cards:0:panel:editor:extension.editor:template:extension.form:template:preview:view:6:item:preview:mixins'
[INFO] [talledLocalContainer] 13.05.2014 12:45:33 ERROR http-bio-8080-exec-4 [DefaultExceptionMapper.internalMap:129] Unexpected error occurred
[INFO] [talledLocalContainer] Unable to find component with id 'mixins' in [MixinLoaderPlugin [Component id = item]]
[INFO] [talledLocalContainer] Expected: 'root:tabs:panel-container:cards:2:panel:center:tabs:panel-container:cards:1:panel:editor:extension.editor:template:view:6:item:mixins'.
[INFO] [talledLocalContainer] Found with similar names: 'root:tabs:panel-container:cards:2:panel:center:tabs:panel-container:cards:0:panel:editor:extension.editor:template:extension.form:template:preview:view:6:item:preview:mixins'
[INFO] [talledLocalContainer] MarkupStream: [markup = jar:file:/home/mathijs/tmp/myhippoproject/target/tomcat7x/webapps/cms/WEB-INF/lib/hippo-cms-editor-frontend-2.26.00.jar!/org/hippoecm/frontend/editor/plugins/mixin/MixinLoaderPlugin.html
[INFO] [talledLocalContainer] <wicket:panel>
[INFO] [talledLocalContainer] <div class="hippo-editor-mixin" wicket:id="mixins"></div>
[INFO] [talledLocalContainer] </wicket:panel>, index = 2, current = '<div class="hippo-editor-mixin" wicket:id="mixins">' (line 0, column 0)]
[INFO] [talledLocalContainer] at org.apache.wicket.markup.MarkupStream.throwMarkupException(MarkupStream.java:526)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1436)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1555)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1530)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalRenderComponent(Component.java:2551)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1494)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalRender(Component.java:2381)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.render(Component.java:2309)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1555)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1530)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.onComponentTagBody(MarkupContainer.java:1485)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.html.panel.DefaultMarkupSourcingStrategy.onComponentTagBody(DefaultMarkupSourcingStrategy.java:71)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalRenderComponent(Component.java:2551)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1494)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalRender(Component.java:2381)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.render(Component.java:2309)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.repeater.AbstractRepeater.renderChild(AbstractRepeater.java:107)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.repeater.AbstractRepeater.onRender(AbstractRepeater.java:94)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalRender(Component.java:2381)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.render(Component.java:2309)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1555)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1530)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalRenderComponent(Component.java:2551)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1494)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalRender(Component.java:2381)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.render(Component.java:2309)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderNext(MarkupContainer.java:1390)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderAll(MarkupContainer.java:1555)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderComponentTagBody(MarkupContainer.java:1530)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.renderAssociatedMarkup(MarkupContainer.java:689)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.html.panel.AssociatedMarkupSourcingStrategy.renderAssociatedMarkup(AssociatedMarkupSourcingStrategy.java:76)
[INFO] [talledLocalContainer] at org.apache.wicket.markup.html.panel.PanelMarkupSourcingStrategy.onComponentTagBody(PanelMarkupSourcingStrategy.java:112)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalRenderComponent(Component.java:2551)
[INFO] [talledLocalContainer] at org.apache.wicket.MarkupContainer.onRender(MarkupContainer.java:1494)
[INFO] [talledLocalContainer] at org.apache.wicket.Component.internalRender(Component.java:2381)