avoid duplication

src/message_api.cc

@@ -50,12 +50,7 @@ namespace pEp {
             int rating = (int) _rating;
             int flags = (int) _flags;
 
-            if (!_dst)
+            Message dst = _dst ? Message(_dst) : Message(src);
-                _dst = ::message_dup(_src);
-            if (!_dst)
-                throw bad_alloc();
-
-            Message dst(_dst);
             return boost::python::make_tuple(dst, keylist, rating, flags);
         }