[gnote] Fix exception in xml_node_xpath_find_single

[Aurimas Äernius <aurimasc src gnome org>]

commit 3d5b34804f6e293a33a5a9d418f6a6246c68ca06
Author: Aurimas Äernius <aurisc4 gmail com>
Date:   Thu Feb 16 16:23:08 2012 +0200

    Fix exception in xml_node_xpath_find_single
    
    Exception is thrown, when nothing is found.

 src/sharp/xml.cpp |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)
---
diff --git a/src/sharp/xml.cpp b/src/sharp/xml.cpp
index ac052cb..c43d07b 100644
--- a/src/sharp/xml.cpp
+++ b/src/sharp/xml.cpp
@@ -77,7 +77,8 @@ namespace sharp {
       return "";
     }
 
-    return reinterpret_cast<char*>(XML_GET_CONTENT(n));
+    char *res = reinterpret_cast<char*>(XML_GET_CONTENT(n));
+    return res ? res : "";
   }