Fixed parsing of empty strings in rare cases for XPath

git-svn-id: http://pugixml.googlecode.com/svn/trunk@171 99668b35-9821-0410-8761-19e4c4f06640

src/pugixpath.cpp

@@ -1086,7 +1086,7 @@ namespace pugi
 
 		const char* contents() const
 		{
-			return m_cur_lexeme_contents;
+			return m_cur_lexeme_contents ? m_cur_lexeme_contents : "";
 		}
 	};