[gnome-builder] plugins/todo: clear panel pointer during unload

[Christian Hergert <chergert src gnome org>]

commit 1c5d8792ad1bc3f1a262ea0ff81c9aa36ce04ebf
Author: Christian Hergert <chergert redhat com>
Date:   Wed Jul 13 09:49:03 2022 -0700

    plugins/todo: clear panel pointer during unload

 src/plugins/todo/gbp-todo-workspace-addin.c | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/src/plugins/todo/gbp-todo-workspace-addin.c b/src/plugins/todo/gbp-todo-workspace-addin.c
index cd84b04c0..aa9c8dde5 100644
--- a/src/plugins/todo/gbp-todo-workspace-addin.c
+++ b/src/plugins/todo/gbp-todo-workspace-addin.c
@@ -176,6 +176,7 @@ gbp_todo_workspace_addin_unload (IdeWorkspaceAddin *addin,
                                         self);
 
   panel_widget_close (PANEL_WIDGET (self->panel));
+  self->panel = NULL;
 
   g_clear_object (&self->model);
   g_clear_object (&self->workdir);