[gtk] Revert "a11y: return -1 if parent is NULL"

[Samuel Thibault <sthibaul src gnome org>]

commit c5786916f764415a5b4979af467ab83cae19bb5d
Author: Samuel Thibault <samuel thibault ens-lyon org>
Date:   Sat Nov 20 10:59:00 2021 +0100

    Revert "a11y: return -1 if parent is NULL"
    
    This reverts commit 22847563cecb59c6f120a08bb49284599dbb6232.

 gtk/a11y/gtkatspicontext.c | 3 ---
 1 file changed, 3 deletions(-)
---
diff --git a/gtk/a11y/gtkatspicontext.c b/gtk/a11y/gtkatspicontext.c
index 43d40ee257..b6bd77b694 100644
--- a/gtk/a11y/gtkatspicontext.c
+++ b/gtk/a11y/gtkatspicontext.c
@@ -334,9 +334,6 @@ get_index_in_parent (GtkWidget *widget)
   GtkWidget *child;
   int idx;
 
-  if (parent == NULL)
-    return -1;
-
   idx = 0;
   for (child = gtk_widget_get_first_child (parent);
        child;