[xdg-desktop-portal-gnome] screencastwidget: Avoid reading destroyed widgets

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 946e91b6dedc3b9b8d403187d316c0c91bcffd9a
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Fri Aug 13 16:10:47 2021 -0300

    screencastwidget: Avoid reading destroyed widgets

 src/screencastwidget.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)
---
diff --git a/src/screencastwidget.c b/src/screencastwidget.c
index 031cf94..a9265b1 100644
--- a/src/screencastwidget.c
+++ b/src/screencastwidget.c
@@ -160,11 +160,13 @@ update_windows_list (ScreenCastWidget *widget)
   GList *windows;
   GList *l;
 
-  for (child = gtk_widget_get_first_child (GTK_WIDGET (window_list));
-       child;
-       child = gtk_widget_get_next_sibling (child))
+  child = gtk_widget_get_first_child (GTK_WIDGET (window_list));
+  while (child)
     {
+      GtkWidget *next = gtk_widget_get_next_sibling (child);
+
       gtk_list_box_remove (window_list, child);
+      child = next;
     }
 
   toplevel = gtk_widget_get_ancestor (GTK_WIDGET (widget), GTK_TYPE_WINDOW);
@@ -193,11 +195,13 @@ update_monitors_list (ScreenCastWidget *widget)
   GList *logical_monitors;
   GList *l;
 
-  for (child = gtk_widget_get_first_child (GTK_WIDGET (monitor_list));
-       child;
-       child = gtk_widget_get_next_sibling (child))
+  child = gtk_widget_get_first_child (GTK_WIDGET (monitor_list));
+  while (child)
     {
+      GtkWidget *next = gtk_widget_get_next_sibling (child);
+
       gtk_list_box_remove (monitor_list, child);
+      child = next;
     }
 
   logical_monitors =