Fix: Nodes: group edit button unintentionally drawn on NodeCustomGroup

Fix regression caused by 6d8d21812b.

Pull Request: https://projects.blender.org/blender/blender/pulls/130204

source/blender/editors/space_node/node_draw.cc

@@ -3424,7 +3424,7 @@ static void node_draw_basis(const bContext &C,
   float iconofs = rct.xmax - 0.35f * U.widget_unit;
 
   /* Group edit. This icon should be the first for the node groups. */
-  if (node.is_group()) {
+  if (node.type == NODE_GROUP) {
     iconofs -= iconbutw;
     UI_block_emboss_set(&block, UI_EMBOSS_NONE);
     uiBut *but = uiDefIconBut(&block,