Bug at the installation.

After the import :
Den.Tools.Serializer.DeserializeObject (System.Int32 refId, Den.Tools.Serializer+Object[] serialized, System.Object[] deserialized, System.Object[] reuse, System.Action`1[T] onBeforeDeserialize) (at Assets/MapMagic/Tools/Serializer.cs:633)
Den.Tools.Serializer.Deserialize (Den.Tools.Serializer+Object[] serialized, System.Action`1[T] onBeforeDeserialize) (at Assets/MapMagic/Tools/Serializer.cs:191)
MapMagic.Nodes.GraphSerializer200Beta.Deserialize (MapMagic.Nodes.Graph graph) (at Assets/MapMagic/Nodes/GraphSerializer.cs:60)
MapMagic.Nodes.Graph.OnAfterDeserialize () (at Assets/MapMagic/Nodes/Graph.cs:1196)

Unity 2021.3.21f1 with HDRP.
URGENT.
Thanks by advance.
Best Regards.
Benjamin.