[gtk/wip/matthiasc/focus2: 46/50] Avoid a critical

[Matthias Clasen <matthiasc src gnome org>]

commit ccb36902e7a0b8bb1d772231df0bba81f437033c
Author: Matthias Clasen <mclasen redhat com>
Date:   Wed Mar 6 23:39:26 2019 -0500

    Avoid a critical

 gtk/gtkwidget.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/gtk/gtkwidget.c b/gtk/gtkwidget.c
index db21c83af0..d0f4d9aba1 100644
--- a/gtk/gtkwidget.c
+++ b/gtk/gtkwidget.c
@@ -7454,6 +7454,9 @@ gtk_widget_child_focus (GtkWidget       *widget,
 
   g_return_val_if_fail (GTK_IS_WIDGET (widget), FALSE);
 
+  if (!gtk_widget_get_root (widget))
+    return FALSE;
+
   focus_child = gtk_root_get_focus (gtk_widget_get_root (widget));
   if (focus_child)
     next_focus = gtk_widget_get_next_focus (focus_child, direction);