2018-09-26 19:12:26,707 INFO rpr.image_cache [10768]:  images: 0, total size: 0.0Mb, requests:0, request per image: -, virtual size requested: 0.0 Mb
2018-09-26 19:12:26,707 INFO rpr.downscaled_image_cache [10768]:  images: 0, total size: 0.0Mb, requests:0, request per image: -, virtual size requested: 0.0 Mb
2018-09-26 19:12:26,708 INFO rpr.core_image_cache [10768]:  CoreImageCache(original): image_size=None, contexts number=0
2018-09-26 19:12:26,708 INFO rpr.core_downscaled_image_cache [10768]:  CoreImageCache(downscaled): image_size=None, contexts number=0
2018-09-26 19:12:26,710 CRITICAL rpr.render [10768]:  ERROR: It is recommended to restart Blender
 Exception: Traceback (most recent call last):
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\render\engine.py", line 103, in render
    self._render(scene)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\helpers.py", line 436, in wrapped
    return f(*argv, **kwargs)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\render\engine.py", line 222, in _render
    for name in scene_exporter.export_iter():
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\export.py", line 770, in export_iter
    yield from self._export_objects(self.scene.objects)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\export.py", line 796, in _export_objects
    yield from self.sync_updated_objects(set(self.visible_objects))
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\export.py", line 1303, in sync_updated_objects
    self.objects_sync.update_material(objects, material)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\export.py", line 281, in update_material
    self.add_material(blender_mat, key)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\helpers.py", line 436, in wrapped
    return f(*argv, **kwargs)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\export.py", line 307, in add_material
    self.scene_synced.add_material(key, blender_mat)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\helpers.py", line 436, in wrapped
    return f(*argv, **kwargs)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\sync.py", line 595, in add_material
    rpr_material.parse(blender_mat)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\core\nodes.py", line 1949, in parse
    self.shader = self.parse_root_node(blender_node)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\core\nodes.py", line 1956, in parse_root_node
    return self.parse_node(None, blender_node)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\core\nodes.py", line 2032, in parse_node
    return registered_nodes[name](blender_node)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\core\nodes.py", line 898, in parse_shader_node_output
    shader = self.parse_node(socket)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\core\nodes.py", line 2032, in parse_node
    return registered_nodes[name](blender_node)
  File "C:\Users\willi\AppData\Roaming\Blender Foundation\Blender\2.79\scripts\addons\rprblender\core\nodes.py", line 1513, in parse_shader_node_pbr3
    if sss_weight_socket.is_linked or sss_weight_socket.default_value:
AttributeError: 'NoneType' object has no attribute 'is_linked'