Don't allow adding Objects to the project settings

Godot doesn't support serializing objects.

This closes #33667.

(cherry picked from commit 7b84f4fc31f40f88575ca7805852d1be9dec3f81)

editor/project_settings_editor.cpp

@@ -1827,9 +1827,12 @@ ProjectSettingsEditor::ProjectSettingsEditor(EditorData *p_data) {
 	type->set_h_size_flags(Control::SIZE_EXPAND_FILL);
 	add_prop_bar->add_child(type);
 
-	// Start at 1 to avoid adding "Nil" as an option
-	for (int i = 1; i < Variant::VARIANT_MAX; i++) {
-		type->add_item(Variant::get_type_name(Variant::Type(i)));
+	for (int i = 0; i < Variant::VARIANT_MAX; i++) {
+		// There's no point in adding Nil types, and Object types
+		// can't be serialized correctly in the project settings.
+		if (i != Variant::NIL && i != Variant::OBJECT) {
+			type->add_item(Variant::get_type_name(Variant::Type(i)));
+		}
 	}
 
 	Button *add = memnew(Button);