diff -r b30dc7db521f -r 57dc2c8ba7c6 src/Pure/GUI/tree_view.scala
--- a/src/Pure/GUI/tree_view.scala	Tue Nov 19 22:41:57 2024 +0100
+++ b/src/Pure/GUI/tree_view.scala	Tue Nov 19 22:48:18 2024 +0100
@@ -53,7 +53,9 @@
 
   /* cell renderer */
 
-  def render_tree_cell(renderer: DefaultTreeCellRenderer): Unit = ()
+  def render_tree_cell(renderer: DefaultTreeCellRenderer): Unit = {
+    renderer.setIcon(null)
+  }
 
   private val tree_cell_renderer: TreeCellRenderer = new DefaultTreeCellRenderer {
     override def getTreeCellRendererComponent(