multi_vfo: fix disconnection

Author: vladisslav2011

src/applications/gqrx/receiver.cpp

@@ -695,9 +695,11 @@ int receiver::delete_rx()
     {
         if (d_current != int(rx.size()) - 1)
         {
+            disconnect_rx(rx.size() - 1);
             rx[d_current] = rx.back();
             rx[d_current]->set_index(d_current);
             rx.back().reset();
+            connect_rx();
         }
         else
             d_current--;