Assert removed/popped elements are not updated fibonacci heap boost

Question

I'm using Boost's Fibonacci heap in my code, and I noticed online it's possible to update an erased/popped element using it's handle: Why can I update a popped out element in a boost::fibonacci_heap?

I have a class wrapping the fib heap and has it's own add, erase, update operations. My question is, what's the best way to enforce a popped/removed element won't be updated?

I store the handle as a member:

typedef boost::heap::fibonacci_heap<EventPtr, boost::heap::compare<sched_events_comp>> fib_heap;

        class Event
        {
          private:
            sched_time_min_t _time;
            sched_event_cb_t _cb;
            fib_heap::handle_type _handle;

            explicit Event(const sched_event_cb_t& cb);

            friend class Sched;
        }

right now this is what I do - when I pop/remove the element I nullify the node:

event->_handle.node_ = nullptr;

when I update an element I assert assert(event->_handle.node_ != nulltptr);. What I don't like is that I change inner members of handle_type which is not implemented by me. I can add another boolean member in my Event class but I'd prefer not to add more members.

what's the best way to assert the element is in the heap before updating (of course in constant time)? thank you!