Merge "Destroy output tracks when existing." into main

        audio_utils::lock_guard l(mutex());

        localTracks = std::move(mOutputTracks);

        mOutputTracks.clear();

        for (size_t i = 0; i < localTracks.size(); ++i) {

            localTracks[i]->destroy();

        }

    }

    localTracks.clear();

    outputTracks.clear();