WIP refactor mesh UI into geometry module and minor fixes. See #1222.

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

@@ -29,7 +29,7 @@ class Usecase:
         if contains_elements:
             related_elements = list(contains_elements[0].RelatedElements)
             related_elements.append(self.settings["product"])
-            contains_elements.RelatedElements = related_elements
+            contains_elements[0].RelatedElements = related_elements
         else:
             contains_elements = self.file.create_entity(
                 "IfcRelContainedInSpatialStructure",

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

@@ -21,13 +21,12 @@ class AssignContainer(bpy.types.Operator):
                 break
         if not relating_structure:
             return {"FINISHED"}
-        usecase = assign_container.Usecase(
+        assign_container.Usecase(
             self.file,
             {
                 "product": self.file.by_id(props.ifc_definition_id),
                 "relating_structure": relating_structure,
             },
-        )
-        usecase.execute()
+        ).execute()
         Data.load(props.ifc_definition_id)
         return {"FINISHED"}