Fix #141948: No error on arbitrary assignments to PropertyGroup

Declare `__slots__` to prevent arbitrary assignment.

scripts/addons_core/bl_pkg/__init__.py

@@ -673,8 +673,7 @@ def cli_extension(argv):
 
 
 class BlExtDummyGroup(bpy.types.PropertyGroup):
-    # Dummy.
-    pass
+    __slots__ = ()
 
 
 # -----------------------------------------------------------------------------

scripts/addons_core/io_scene_gltf2/__init__.py

@@ -2113,6 +2113,8 @@ def import_panel_user_extension(context, layout):
 
 
 class GLTF2_filter_action(bpy.types.PropertyGroup):
+    __slots__ = ()
+
     keep: bpy.props.BoolProperty(name="Keep Animation")
     action: bpy.props.PointerProperty(type=bpy.types.Action)
 

scripts/startup/bl_operators/bone_selection_sets.py

@@ -25,10 +25,14 @@ from bpy.props import (
 
 
 class SelectionEntry(PropertyGroup):
+    __slots__ = ()
+
     name: StringProperty(name="Bone Name", override={'LIBRARY_OVERRIDABLE'})
 
 
 class SelectionSet(PropertyGroup):
+    __slots__ = ()
+
     name: StringProperty(name="Set Name", override={'LIBRARY_OVERRIDABLE'})
     bone_ids: CollectionProperty(
         type=SelectionEntry,

scripts/startup/bl_operators/node.py

@@ -29,6 +29,8 @@ from bpy.app.translations import (
 
 
 class NodeSetting(PropertyGroup):
+    __slots__ = ()
+
     value: StringProperty(
         name="Value",
         description="Python expression to be evaluated "

scripts/startup/bl_operators/wm.py

@@ -2665,6 +2665,8 @@ class WM_OT_toolbar_prompt(Operator):
 
 
 class BatchRenameAction(bpy.types.PropertyGroup):
+    __slots__ = ()
+
     # category: StringProperty()
     type: EnumProperty(
         name="Operation",