fix layer delete

engine/app_layout.cpp

@@ -96,6 +96,10 @@ void App::initLayout()
             canvas->m_canvas->layer_order(old_idx, new_idx);
         };
 
+        layers->on_layer_delete = [this](Node*, int idx) {
+            canvas->m_canvas->layer_remove(canvas->m_canvas->m_order[idx]);
+        };
+
         layers->on_layer_opacity_changed = [this](Node*, int idx, float value) {
             canvas->m_canvas->m_layers[canvas->m_canvas->m_order[idx]].m_opacity = value;
         };