[glom] libxml++-3.0 port: Case the Attribute to an AttributeNode.

[Murray Cumming <murrayc src gnome org>]

commit 029371e4fcec5d05b2d47beb0ba795455b49a487
Author: Murray Cumming <murrayc murrayc com>
Date:   Sat Oct 24 20:04:31 2015 +0200

    libxml++-3.0 port: Case the Attribute to an AttributeNode.

 glom/libglom/xml_utils.cc |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/glom/libglom/xml_utils.cc b/glom/libglom/xml_utils.cc
index 87dddbf..040148a 100644
--- a/glom/libglom/xml_utils.cc
+++ b/glom/libglom/xml_utils.cc
@@ -50,7 +50,7 @@ void set_node_attribute_value(xmlpp::Element* node, const Glib::ustring& strAttr
 {
   if(node)
   {
-    auto attribute = node->get_attribute(strAttributeName);
+    auto attribute = dynamic_cast<xmlpp::AttributeNode*>(node->get_attribute(strAttributeName));
     if(attribute)
       attribute->set_value(strValue);
     else