[gtk+] Avoid criticals in gtk_image_get_render_node

[Matthias Clasen <matthiasc src gnome org>]

commit 7b2313a6df3bc8c9b3c25dbea319051b3d9cd789
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Nov 10 08:26:37 2016 -0500

    Avoid criticals in gtk_image_get_render_node
    
    These nodes can be NULL, we need to handle that.

 gtk/gtkimage.c |    7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)
---
diff --git a/gtk/gtkimage.c b/gtk/gtkimage.c
index 7d5e99f..612b337 100644
--- a/gtk/gtkimage.c
+++ b/gtk/gtkimage.c
@@ -1458,8 +1458,11 @@ gtk_image_get_render_node (GtkWidget   *widget,
       node = gtk_icon_helper_get_render_node (priv->icon_helper, renderer);
     }
 
-  gsk_render_node_append_child (res, node);
-  gsk_render_node_unref (node);
+  if (node != NULL)
+    {
+      gsk_render_node_append_child (res, node);
+      gsk_render_node_unref (node);
+    }
 
   return res;
 }