fixup

Author: jngrad

src/core/MpiCallbacks.hpp

@@ -203,7 +203,7 @@ class MpiCallbacks {
                               typename detail::functor_types<F>::argument_types,
                               std::tuple<Args...>>>>
     CallbackHandle(std::shared_ptr<MpiCallbacks> cb, F &&f)
-        : m_id(cb->add(std::forward<F>(f))), m_cb(cb) {}
+        : m_id(cb->add(std::forward<F>(f))), m_cb(std::move(cb)) {}
 
     CallbackHandle(CallbackHandle const &) = delete;
     CallbackHandle(CallbackHandle &&rhs) noexcept = default;