G-code Queue followup (#21214)

Marlin/src/gcode/sd/M28_M29.cpp

     // Binary transfer mode
     if ((card.flag.binary_mode = binary_mode)) {
       SERIAL_ECHO_MSG("Switching to Binary Protocol");
-      TERN_(HAS_MULTI_SERIAL, card.transfer_port_index = queue.port[queue.index_r]);
+      TERN_(HAS_MULTI_SERIAL, card.transfer_port_index = queue.ring_buffer.command_port());
     }
     else
       card.openFileWrite(p);