[libxml++] Node: Move the null-pointer check to the constructor.

[Kjell Ahlstedt <kjellahl src gnome org>]

commit dab34672a5a06641a9f56922a7d4eaefa55b9627
Author: Kjell Ahlstedt <kjell ahlstedt bredband net>
Date:   Mon Aug 12 16:35:03 2013 +0200

    Node: Move the null-pointer check to the constructor.
    
    * libxml++/nodes/node.[h|cc]: Let the constructor throw xmlpp:internal_error
    if impl_ == 0. Remove other null-pointer checks. Bug #705187.

 libxml++/nodes/node.cc |   11 ++++-------
 libxml++/nodes/node.h  |    2 ++
 2 files changed, 6 insertions(+), 7 deletions(-)
---
diff --git a/libxml++/nodes/node.cc b/libxml++/nodes/node.cc
index 325b9d0..c35bd16 100644
--- a/libxml++/nodes/node.cc
+++ b/libxml++/nodes/node.cc
@@ -119,7 +119,10 @@ namespace xmlpp
 Node::Node(xmlNode* node)
   : impl_(node)
 {
-   impl_->_private = this;
+  if (!impl_)
+    throw internal_error("xmlNode pointer cannot be 0");
+
+  impl_->_private = this;
 }
 
 Node::~Node()
@@ -510,9 +513,6 @@ Glib::ustring Node::eval_to_string(const Glib::ustring& xpath, const PrefixNsMap
 
 Glib::ustring Node::get_namespace_prefix() const
 {
-  if(!impl_)
-    return Glib::ustring();
-
   if(impl_->type == XML_DOCUMENT_NODE || impl_->type == XML_ENTITY_DECL)
   {
     //impl_ is actually of type xmlDoc or xmlEntity, instead of just xmlNode.
@@ -538,9 +538,6 @@ Glib::ustring Node::get_namespace_prefix() const
 
 Glib::ustring Node::get_namespace_uri() const
 {
-  if(!impl_)
-    return Glib::ustring();
-
   if(impl_->type == XML_DOCUMENT_NODE ||
      impl_->type == XML_ENTITY_DECL ||
      impl_->type == XML_ATTRIBUTE_DECL)
diff --git a/libxml++/nodes/node.h b/libxml++/nodes/node.h
index a60107e..6a02ecf 100644
--- a/libxml++/nodes/node.h
+++ b/libxml++/nodes/node.h
@@ -55,6 +55,8 @@ class Node : public NonCopyable
 public:
   typedef std::list<Node*> NodeList;
 
+  /** @throws xmlpp::internal_error If @a node is <tt>0</tt>.
+   */
   explicit Node(_xmlNode* node);
   virtual ~Node();