GtkWidget: Handle style updates before realize

If the style changes before we're realized we will delay the
style-updated signal until realize. However, we then lose
the changes bitmap. This means that gtk_widget_real_style_updated()
must treat a NULL change as "everything changed" and queue a resize.

gtk/gtkwidget.c

@@ -7145,7 +7145,7 @@ gtk_widget_real_style_updated (GtkWidget *widget)
 
       if (widget->priv->anchored)
         {
-          if (changes && _gtk_css_style_property_changes_affect_size (changes))
+          if (changes == NULL || _gtk_css_style_property_changes_affect_size (changes))
             gtk_widget_queue_resize (widget);
           else
             gtk_widget_queue_draw (widget);