Error when saving page with new elements for text item type

I am adding elements and modifying the descriptions of existing elements for the item type "person" and I received this message. Is there a way to go backwards/undo my modifications and try again? Or can someone tell me what this means?


Item type does not contain an element with the ID 31!

#0 /home/katiebercury/ ItemType->_removeElement(Object(Element))
#1 [internal function]: ItemType->afterSave(Array)
#2 /home/katiebercury/ call_user_func(Array, Array)
#3 /home/katiebercury/ Omeka_Record_AbstractRecord->runCallbacks('afterSave', Array)
#4 /home/katiebercury/ Omeka_Record_AbstractRecord->save()
#5 /home/katiebercury/ Omeka_Form_ItemTypes->saveFromPost()
#6 /home/katiebercury/ ItemTypesController->editAction()
#7 /home/katiebercury/ Zend_Controller_Action->dispatch('editAction')
#8 /home/katiebercury/ Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))
#9 /home/katiebercury/ Zend_Controller_Front->dispatch()
#10 /home/katiebercury/ Zend_Application_Bootstrap_Bootstrap->run()
#11 /home/katiebercury/ Zend_Application->run()
#12 /home/katiebercury/ Omeka_Application->run()
#13 {main}

This is not a huge problem. I'm still curious and would like to understand what was happening but have been able to go forward and it hasn't popped up again.

You get that error when you try to remove an Element that's not (or no longer is) part of the Item Type that you're editing.

If you had made a change and went back and/or refreshed the page, you could have been trying to make the same change again, causing this error.