[gxml/serialization] Added check for serializable node name is null.

[Daniel Espinosa Ortiz <despinosa src gnome org>]

commit c1f7db13c3f2bf7053e0d1c0b24f963445debab2
Author: Daniel Espinosa <esodan gmail com>
Date:   Wed Nov 6 18:42:12 2013 -0600

    Added check for serializable node name is null.

 gxml/SerializableObjectModel.vala |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)
---
diff --git a/gxml/SerializableObjectModel.vala b/gxml/SerializableObjectModel.vala
index 9d6a14d..c312cf3 100644
--- a/gxml/SerializableObjectModel.vala
+++ b/gxml/SerializableObjectModel.vala
@@ -181,6 +181,8 @@ public abstract class GXml.SerializableObjectModel : Object, Serializable
                        element = (Element) node;
                else
                        element = (Element) doc.document_element;
+               return_val_if_fail (element != null, null);
+               return_val_if_fail (serializable_node_name != null, null);
                return_val_if_fail (element.node_name.down () == serializable_node_name.down (), null);
                foreach (Attr attr in element.attributes.get_values ())
                {