add template Node::clone() and remove destroy_immediate

src/node_stroke_preview.cpp

@@ -589,10 +589,10 @@ void NodeStrokePreview::handle_resize(glm::vec2 old_size, glm::vec2 new_size, fl
         draw_stroke();
 }
 
-void NodeStrokePreview::destroy_immediate()
+void NodeStrokePreview::destroy()
 {
-    Node::destroy_immediate();
     m_tex_preview.destroy();
+    Node::destroy();
 }
 
 void NodeStrokePreview::handle_on_screen(bool old_visibility, bool new_visibility)