WIP migrate attribute management to partial editing with 4 new features! See #1222.

New features include:

 - New clarity between null and empty string attributes
 - Attribute editing now shows appropriate UI widgets depending on data type
 - Attribute editing for enumerations now show a dropdown
 - Attribute editing is now schema sensitive

src/ifcblenderexport/blenderbim/bim/module/spatial/data.py

@@ -10,7 +10,9 @@ class Data:
         if not file:
             return
         product = file.by_id(product_id)
-        if product.ContainedInStructure:
+        if not hasattr(product, "ContainedInStructure"):
+            cls.products[product_id] = None
+        elif product.ContainedInStructure:
             structure = product.ContainedInStructure[0].RelatingStructure
             cls.products[product_id] = {"type": structure.is_a(), "Name": structure.Name, "id": int(structure.id())}
         else: