fix: nullable workbench

Author: giancarloromeo

packages/models-library/src/models_library/projects.py

@@ -109,7 +109,9 @@ class BaseProjectModel(BaseModel):
     # Pipeline of nodes (SEE projects_nodes.py)
     # FIXME: pedro checks this one
     # NOTE: GCG: a validation failed (See: services/storage/src/simcore_service_storage/modules/db/projects.py)
-    # workbench: Annotated[NodesDict, Field(description="Project's pipeline")]
+    workbench: Annotated[NodesDict, Field(description="Project's pipeline")] | None = (
+        None
+    )
 
 
 class ProjectAtDB(BaseProjectModel):