Fix polygon node losing its UV toolbar by adding a call to the show m…

…ethod when assinging a node.

Fixes godotengine#96238

(cherry picked from commit dabeaa6)

editor/plugins/abstract_polygon_2d_editor.cpp

@@ -751,7 +751,9 @@ AbstractPolygon2DEditor::AbstractPolygon2DEditor(bool p_wip_destructive) {
 }
 
 void AbstractPolygon2DEditorPlugin::edit(Object *p_object) {
-	polygon_editor->edit(Object::cast_to<Node>(p_object));
+	Node *polygon_node = Object::cast_to<Node>(p_object);
+	polygon_editor->edit(polygon_node);
+	make_visible(polygon_node != nullptr);
 }
 
 bool AbstractPolygon2DEditorPlugin::handles(Object *p_object) const {