[gtk/scrollbar-a11y] scrollbar: Be more defensive

[Matthias Clasen <matthiasc src gnome org>]

commit 5205fa0ff7635154a76e7c810bfc00cf041029ca
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri Apr 3 23:31:45 2020 -0400

    scrollbar: Be more defensive
    
    Somehow the scrollbar accessible manages to call
    gtk_scrollbar_get_adjustment when priv->range is NULL.
    Survive taht.

 gtk/gtkscrollbar.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
---
diff --git a/gtk/gtkscrollbar.c b/gtk/gtkscrollbar.c
index 97730e1eea..84b18c02dc 100644
--- a/gtk/gtkscrollbar.c
+++ b/gtk/gtkscrollbar.c
@@ -285,5 +285,8 @@ gtk_scrollbar_get_adjustment (GtkScrollbar  *self)
 
   g_return_val_if_fail (GTK_IS_SCROLLBAR (self), NULL);
 
-  return gtk_range_get_adjustment (GTK_RANGE (priv->range));
+  if (priv->range)
+    return gtk_range_get_adjustment (GTK_RANGE (priv->range));
+
+  return NULL;
 }