ERP5Workflow: add possibility to choose no destination state in Transition view

bt5/erp5_workflow/SkinTemplateItem/portal_skins/erp5_workflow/Transition_view/my_destination.xml

@@ -269,7 +269,7 @@
       <dictionary>
         <item>
             <key> <string>_text</string> </key>
-            <value> <string>python: [(x.getTitle(), x.getRelativeUrl()) for x in here.getParent().contentValues(filter={\'portal_type\': \'State\'})]</string> </value>
+            <value> <string>python: [(x.getTitle(), x.getRelativeUrl()) for x in here.getParentValue().objectValues(portal_type=\'State\')] + [\'\']</string> </value>
         </item>
       </dictionary>
     </pickle>