[libpanel] dock: fix iteration to locate dock child widgets

[Christian Hergert <chergert src gnome org>]

commit 719a411423c81f3c821eeca054d13d8f33b83575
Author: Christian Hergert <chergert redhat com>
Date:   Fri Sep 16 19:21:47 2022 -0700

    dock: fix iteration to locate dock child widgets

 src/panel-dock.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
---
diff --git a/src/panel-dock.c b/src/panel-dock.c
index 6f9d8e7..76577d9 100644
--- a/src/panel-dock.c
+++ b/src/panel-dock.c
@@ -1258,9 +1258,11 @@ panel_dock_set_panel_size (PanelDock *self,
                            PanelArea  area,
                            int        size)
 {
+  PanelDockPrivate *priv = panel_dock_get_instance_private (self);
+
   g_return_if_fail (PANEL_IS_DOCK (self));
 
-  for (GtkWidget *child = gtk_widget_get_first_child (GTK_WIDGET (self));
+  for (GtkWidget *child = gtk_widget_get_first_child (GTK_WIDGET (priv->grid));
        child;
        child = gtk_widget_get_next_sibling (child))
     {