Object sockets - ReferenceError

[Durman]

Problem statement

2020-12-11 21:49:31,077 [ERROR] sverchok.core.update_system: Node Assign Materials List had exception: StructRNA of type Object has been removed
Traceback (most recent call last):
  File ".\sverchok\core\update_system.py", line 384, in do_update_general
    node.process()
  File ".\sverchok\nodes\object_nodes\assign_materials.py", line 164, in process
    objects = self.inputs['Object'].sv_get()
  File ".\sverchok\core\sockets.py", line 374, in sv_get
    return self.convert_data(SvGetSocket(self, deepcopy), implicit_conversions)
  File ".\sverchok\core\socket_data.py", line 115, in SvGetSocket
    return sv_deep_copy(out)
  File ".\sverchok\core\socket_data.py", line 40, in sv_deep_copy
    if lst and not isinstance(lst[0], (list, tuple)):
ReferenceError: StructRNA of type Object has been removed

Steps to reproduce

1. Make any action and press Ctrl+z
2. Add new item to assign material list

Looks like problem with object sockets.