message: Remove undefined behaviour from raft_test (again)
diff: @@ -73,6 +73,7 @@ static size_t dispatch_all_and_DOCTEST_CHECK(
  auto [tgt_node_id, contents] = messages.front();
  messages.pop_front();
  + if constexpr (!std::is_same_v<AssertionArg, void>)
  {
  AssertionArg arg = *(AssertionArg*)contents.data();
  assertion(arg);
  @@ -100,7 +101,7 @@ static size_t dispatch_all(
  const ccf::NodeId& from,
  aft::ChannelStubProxy::MessageList& messages)
  {
  - return dispatch_all_and_DOCTEST_CHECK<bool>(
  + return dispatch_all_and_DOCTEST_CHECK<void>(
  nodes, from, messages, [](const auto&) {
  // Pass
  });
  