Fix ObjectDB Instances still exist

```
WARNING: cleanup: ObjectDB Instances still exist!
   At: core/object.cpp:1989.
Leaked Instance: VSeparator:13837 - Node Name:
Leaked Instance: AutotileEditorHelper:13814
Orphan StringName: VSeparator
Orphan StringName: AutotileEditorHelper
StringName: 2 unclaimed string names at exit.
```

editor/plugins/tile_set_editor_plugin.cpp

@@ -420,7 +420,7 @@ AutotileEditor::AutotileEditor(EditorNode *p_editor) {
 	p.push_back((int)SHAPE_DELETE);
 	tools[SHAPE_DELETE]->connect("pressed", this, "_on_tool_clicked", p);
 	tool_containers[TOOLBAR_SHAPE]->add_child(tools[SHAPE_DELETE]);
-	tool_containers[TOOLBAR_SHAPE]->add_change_receptor(memnew(VSeparator));
+	tool_containers[TOOLBAR_SHAPE]->add_child(memnew(VSeparator));
 	tools[SHAPE_KEEP_INSIDE_TILE] = memnew(ToolButton);
 	tools[SHAPE_KEEP_INSIDE_TILE]->set_toggle_mode(true);
 	tools[SHAPE_KEEP_INSIDE_TILE]->set_pressed(true);
@@ -548,6 +548,10 @@ AutotileEditor::AutotileEditor(EditorNode *p_editor) {
 	preview->set_region(true);
 }
 
+AutotileEditor::~AutotileEditor() {
+	memdelete(helper);
+}
+
 void AutotileEditor::_bind_methods() {
 
 	ClassDB::bind_method("_on_autotile_selected", &AutotileEditor::_on_autotile_selected);

editor/plugins/tile_set_editor_plugin.h

@@ -120,6 +120,7 @@ class AutotileEditor : public Control {
 	AutotileEditorHelper *helper;
 
 	AutotileEditor(EditorNode *p_editor);
+	~AutotileEditor();
 
 protected:
 	static void _bind_methods();