BIM: fix deletion of BuildingPart in strict IFC mode (#26219)

* BIM: fix deletion of BuildingPart in strict IFC mode

Add `sg = FreeCADGui.ActiveDocument.ActiveView.getSceneGraph()` to `onDelete`.

* BIM: fix deletion of BuildingPart in strict IFC mode

Explicitly call `obj.ViewObject.Proxy.attach(obj.ViewObject)`.

* BIM: fix deletion of BuildingPart in strict IFC mode

In `ifc_vp_buildingpart` call `attach` from `ArchBuildingPart.ViewProviderBuildingPart`.

src/Mod/BIM/ArchBuildingPart.py

@@ -1112,6 +1112,7 @@ class ViewProviderBuildingPart:
     def onDelete(self, vobj, subelements):
 
         if self.clip:
+            sg = FreeCADGui.ActiveDocument.ActiveView.getSceneGraph()
             sg.removeChild(self.clip)
             self.clip = None
         for o in Draft.get_group_contents(vobj.Object.Group, walls=True):

src/Mod/BIM/nativeifc/ifc_tools.py

@@ -575,6 +575,7 @@ def add_object(document, otype=None, oname="IfcObject"):
             obj.ViewObject.ShowLevel = False
             obj.ViewObject.ShowLabel = False
             obj.ViewObject.Proxy = ifc_viewproviders.ifc_vp_buildingpart(obj.ViewObject)
+            obj.ViewObject.Proxy.attach(obj.ViewObject)
         for p in obj.PropertiesList:
             if obj.getGroupOfProperty(p) in ["BuildingPart", "IFC Attributes", "Children"]:
                 obj.removeProperty(p)

src/Mod/BIM/nativeifc/ifc_viewproviders.py

@@ -620,6 +620,9 @@ class ifc_vp_buildingpart(ifc_vp_object, ArchBuildingPart.ViewProviderBuildingPa
     def __init__(self, vobj):
         ArchBuildingPart.ViewProviderBuildingPart.__init__(self, vobj)
 
+    def attach(self, vobj):
+        ArchBuildingPart.ViewProviderBuildingPart.attach(self, vobj)
+
 
 def overlay(icon1, icon2):
     """Overlays icon2 onto icon1"""