fix: optimization: PVS-Studio warning V832

It's better to use '= default;' syntax instead of empty constructor and destructor body.
Using '= default;' can help the compiler generate more optimal code.

Reported by: PVS-Studio

Signed-off-by: Vyacheslav Ivanov <islavaivanov76@gmail.com>

src/coders/xml.hpp

@@ -23,7 +23,7 @@ namespace xml {
         std::string name;
         std::string text;
     public:
-        Attribute() {};
+        Attribute() = default;
         Attribute(std::string name, std::string text);
 
         const std::string& getName() const;