don't bother with immediate_view if we didn't get an object (#4468)

plone/dexterity/browser/add.py

@@ -76,6 +76,8 @@ class DefaultAddForm(DexterityExtensibleForm, form.AddForm):
         fti = getUtility(IDexterityFTI, name=self.portal_type)
         container = aq_inner(self.context)
         new_object = addContentToContainer(container, object)
+        if new_object is None:
+            return
         
         if fti.immediate_view:
             self.immediate_view = "%s/%s/%s" % (container.absolute_url(), new_object.id, fti.immediate_view,)