Avoid null pointer dereference am: ee3b08f2 am: 219561fb

          LeAudioClientAudioSink::SendData((uint8_t*)left->data(), to_write);

    } else if (!bt_got_stereo && af_is_stereo) {

      /* mono audio over bluetooth, audio framework expects stereo */

      std::vector<uint16_t> mixed(left ? left->size() * 2 : right->size() * 2);

      const size_t mono_size = left ? left->size() : right->size();

      std::vector<uint16_t> mixed(mono_size * 2);

      for (size_t i = 0; i < left->size(); i++) {

      for (size_t i = 0; i < mono_size; i++) {

        mixed[2 * i] = left ? (*left)[i] : 0;

        mixed[2 * i + 1] = right ? (*right)[i] : 0;

      }