Code review comment for lp:~widelands-dev/widelands/refactor_gameclient

Still get a heap-use-after-free related to
    std::unique_ptr<UI::ProgressWindow> loader_ui(new UI::ProgressWindow());

But this is maybe just a problem as the game crashed with disconnect(CLIENT_CRASHED, )

A have a deja vue around GameClientImpl.modal which is released twice.