cubicweb #4354551 crash on form validation [validation pending]

I got the following crash when trying to validate a form.

2014-09-15 09:06:42 - (cubicweb.web) ERROR: unexpected error while validating form
Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/basecontrollers.py", line 216, in _validate_form
ctrl.publish(None)
File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/editcontroller.py", line 127, in publish
return callback()
File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/editcontroller.py", line 366, in _action_apply
self._default_publish()
File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/editcontroller.py", line 203, in _default_publish
self.handle_formfield(form_, field)
File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/editcontroller.py", line 285, in handle_formfield
for field, value in field.process_posted(form):
File "/usr/lib/python2.7/dist-packages/cubicweb/web/formfields.py", line 497, in process_posted
value = field.process_form_value(form)
File "/usr/lib/python2.7/dist-packages/cubicweb/web/formfields.py", line 1138, in process_form_value
value = self._process_form_value(form)
File "/usr/lib/python2.7/dist-packages/cubicweb/web/formfields.py", line 1166, in _process_form_value
form._cw.data['pending_others'].add( (form, self) )
KeyError: 'pending_others'

by that point the controller has pop()ed the pending_others key from req.data.

prioritynormal
typebug
done in3.24.0
load left0.000
closed by#8f264d98d6fd [web] Clear "pending_others" session key after all relations got processed
patch[web] Clear "pending_others" session key after all relations got processed [applied]