The user uses the following code that breaks :

EventHook m_eventHook;
void Start()
{
m_eventHook = new EventHook("DoWork");
EventBus.Register<int>(m_eventHook, DoWork);
}

private void Update()
{
if (m_eventHook != null)
{
EventBus.Trigger(m_eventHook, 1);
}
}
But EvenHook is a struct and structs are value types. This means it cannot be null and when checking if the eventHook is null it falls back on a default implicit operator which is by design. If users want to check if the EventHook is null they must use the Nullable Value Types C#8 feature. Here is how the code should look like:

EventHook? m_eventHook;
void Start()
{
m_eventHook = new EventHook("DoWork");
EventBus.Register<int>(m_eventHook.Value, DoWork);
}

private void Update()
{
if (m_eventHook != null)
{
EventBus.Trigger(m_eventHook.Value, 1);
}
}