Fix #7158. UI didn't expect to find a material constituent set with no constituents.

It's technically valid but makes no sense.

src/bonsai/bonsai/bim/module/material/data.py

@@ -404,7 +404,7 @@ class ObjectMaterialData:
         material = cls.material
         if not cls.material or not material.is_a("IfcMaterialConstituentSet"):
             return []
-        return [m.Name for m in material.MaterialConstituents if m.Name]
+        return [m.Name for m in material.MaterialConstituents or [] if m.Name]
 
     @classmethod
     def is_type_material_overridden(cls) -> bool:

src/bonsai/bonsai/bim/module/material/ui.py

@@ -254,6 +254,10 @@ class BIM_PT_object_material(Panel):
         active_object = bpy.context.active_object
         self.layerset_bounds(box, active_object, location="Top_Exterior")
 
+        if not ObjectMaterialData.data["set_items"]:
+            row = box.row()
+            row.label(text="No Materials Found")
+
         for set_item in ObjectMaterialData.data["set_items"]:
             if (
                 len(self.props.material_set_item_profile_attributes)
@@ -357,6 +361,10 @@ class BIM_PT_object_material(Panel):
         active_object = bpy.context.active_object
         self.layerset_bounds(box, active_object, location="Top_Interior")
 
+        if not ObjectMaterialData.data["set_items"]:
+            row = box.row()
+            row.label(text="No Materials Found")
+
         for set_item in ObjectMaterialData.data["set_items"]:
             material_name = set_item["material"]
             material_id = set_item["material_id"]