[gnome-sudoku] Fix redundant undo entries for earmarks

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 93eaf8d21bc28633bf31503713b4003b63226a8f
Author: Steven Elliott <selliott512 gmail com>
Date:   Fri Jul 8 13:30:23 2022 +0000

    Fix redundant undo entries for earmarks

 src/sudoku-view.vala | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/src/sudoku-view.vala b/src/sudoku-view.vala
index 25c26bf..1c0da5e 100644
--- a/src/sudoku-view.vala
+++ b/src/sudoku-view.vala
@@ -162,10 +162,12 @@ private class SudokuCellView : DrawingArea
     {
         earmark_picker = new NumberPicker (ref game.board, true);
         earmark_picker.earmark_state_changed.connect ((number, state) => {
+            // For enable and disable the "board" is written to directly to
+            // avoid affecting the undo stack.
             if (state)
-                this.game.enable_earmark (row, col, number);
+                this.game.board.enable_earmark (row, col, number);
             else
-                this.game.disable_earmark (row, col, number);
+                this.game.board.disable_earmark (row, col, number);
             this.game.cell_changed (row, col, value, value);
             queue_draw ();
         });