Traceback (most recent call last):
  File "/trytond/protocols/jsonrpc.py", line 123, in _marshaled_dispatch
    response['result'] = dispatch_method(method, params)
  File "/trytond/protocols/jsonrpc.py", line 156, in _dispatch
    res = dispatch(*args)
  File "/trytond/protocols/dispatcher.py", line 163, in dispatch
    result = rpc.result(meth(inst, *args, **kwargs))
  File "/trytond/modules/Goods_Receipts/Goods_Receipts_Transfer.py", line 461, in on_change_pendingrppp
    M2Mdic['category'] = str(xxx.selectedstocknumber.category)
  File "/trytond/model/modelstorage.py", line 1209, in __getattr__
    raise AttributeError('"%s" has no attribute "%s"' % (self, name))
AttributeError: "upr.upr,1" has no attribute "selectedstocknumber"