Protocols.HTTP: KeptConnection()s may outlast their Session()

lib/modules/Protocols.pmod/HTTP.pmod/Session.pike

@@ -640,17 +640,21 @@ protected class KeptConnection
    }
 
    void disconnect()
+   {
+      if (global::this)
       {
          Thread.MutexKey key = connection_cache_mux->lock(2);
+
          connection_cache[lookup]-=({this});
          if (!sizeof(connection_cache[lookup]))
             m_delete(connection_cache,lookup);
          remove_call_out(disconnect); // if called externally
-
-      if (q && q->con) {q->con->close(); destruct(q->con);}
          connections_kept_n--;
          if (!--connections_host_n[lookup])
             m_delete(connections_host_n,lookup);
+      }
+
+      if (q && q->con) {q->con->close(); destruct(q->con);}
       destruct(q);
       destruct(this);
    }