stream: reset subscription's stream pointer in stream's destructor

core/stream.hh

@@ -41,6 +41,7 @@ public:
     stream() = default;
     stream(const stream&) = delete;
     stream(stream&&) = delete;
+    ~stream();
     void operator=(const stream&) = delete;
     void operator=(stream&&) = delete;
 
@@ -93,6 +94,15 @@ public:
     friend class stream<T...>;
 };
 
+
+template <typename... T>
+inline
+stream<T...>::~stream() {
+    if (_sub) {
+        _sub->_stream = nullptr;
+    }
+}
+
 template <typename... T>
 inline
 subscription<T...>