Fixed error when creating physical skeleton

An error was systematically triggered on the root bone, when trying to access its parent (the return value wasn't used in this case anyway).

Fixes #23920

editor/plugins/skeleton_editor_plugin.cpp

@@ -65,7 +65,6 @@ void SkeletonEditor::create_physical_skeleton() {
 	for (int bone_id = 0; bc > bone_id; ++bone_id) {
 
 		const int parent = skeleton->get_bone_parent(bone_id);
-		const int parent_parent = skeleton->get_bone_parent(parent);
 
 		if (parent < 0) {
 
@@ -73,6 +72,8 @@ void SkeletonEditor::create_physical_skeleton() {
 
 		} else {
 
+			const int parent_parent = skeleton->get_bone_parent(parent);
+
 			bones_infos.write[bone_id].relative_rest = bones_infos[parent].relative_rest * skeleton->get_bone_rest(bone_id);
 
 			/// create physical bone on parent