It's not working anymore!

Greetings
The sample project isn't working anymore ... Many of the AudioKit's APIs have changed since then. I've actually read the AudioKit's migration guide & changed the Conductor accordingly:
import AudioKit
import Foundation

/// The persistent data object of the application (it does the audio processing and publishes changes to the UI)
final class Conductor : ObservableObject {

    /// Single shared data model
    static let shared = Conductor()

    /// default microphone
//    let mic = Microphone()
    let engine = AudioEngine()
    // No usage for now?
    static let player = AudioPlayer()

    let mic: AudioEngine.InputNode

    /// mixing node for microphone input - routes to plotting and recording paths
    let micMixer = Mixer()

    /// time interval in seconds for repeating timer callback
    let refreshTimeInterval : Double = 0.02

    /// tap for the fft data
    let fft : FFTTap

    /// size of fft
    let FFT_SIZE = 512

    /// audio sample rate
    let sampleRate: double_t = 44100

    /// limiter to prevent excessive volume at the output - just in case, it's the music producer in me :)
    let outputLimiter = PeakLimiter(player)

    /// bin amplitude values (range from 0.0 to 1.0)
    @Published var amplitudes: [Double] = Array(repeating: 0.5, count: 50)

    /// constructor - runs during initialization of the object
    init(){

        // connect the fft tap to the mic mixer (this allows us to analyze the audio at the micMixer node)
        fft = FFTTap.init(micMixer, handler: { _ in })

        // route the audio from the microphone to the limiter
//        setupMic()

        // set the limiter as the last node in our audio chain
        engine.output = outputLimiter

        self.mic = engine.input ?? .init()

        // do any AudioKit setting changes before starting the AudioKit engine
        setAudioKitSettings()

        // start the AudioKit engine
        do {
            try engine.start()
        }
        catch {
            assert(false, error.localizedDescription)
        }

        // create a repeating timer at the rate of our chosen time interval - this updates the amplitudes each timer callback
        Timer.scheduledTimer(withTimeInterval: refreshTimeInterval, repeats: true) { timer in
            self.updateAmplitudes()
        }

    }

    /// Sets AudioKit to appropriate settings
    func setAudioKitSettings(){

        do {
            try Settings.setSession(category: .ambient, with: [.mixWithOthers])
        } catch {
            Log("Could not set session category.")
        }

    }

    /*
    /// Does all the setup required for microphone input
    func setupMic() {

        // route mic to the micMixer which is tapped by our fft
        mic?.setOutput(to: micMixer)

        // route mixMixer to a mixer with no volume so that we don't output audio
        let silentMixer = Mixer(micMixer)
        silentMixer.volume = 0.0

        // route the silent Mixer to the limiter (you must always route the audio chain to AudioKit.output)
        silentMixer.setOutput(to: outputLimiter)

    }
     */

    /// Analyze fft data and write to our amplitudes array
    @objc func updateAmplitudes(){
        //If you are interested in knowing more about this calculation, I have provided a couple recommended links at the bottom of this file.

        // loop by two through all the fft data
        for i in stride(from: 0, to: self.FFT_SIZE - 1, by: 2) {

            // get the real and imaginary parts of the complex number
            let real = fft.fftData[i]
            let imaginary = fft.fftData[i + 1]

            let normalizedBinMagnitude = 2.0 * sqrt(real * real + imaginary * imaginary) / self.FFT_SIZE
            let amplitude = (20.0 * log10(10/*normalizedBinMagnitude*/))

            // scale the resulting data
            var scaledAmplitude = (amplitude + 250) / 229.80

            // restrict the range to 0.0 - 1.0
            if (scaledAmplitude < 0) {
                scaledAmplitude = 0
            }
            if (scaledAmplitude > 1.0) {
                scaledAmplitude = 1.0
            }

            // add the amplitude to our array (further scaling array to look good in visualizer)
            DispatchQueue.main.async {
                if(i/2 < self.amplitudes.count){
                    self.amplitudes[i/2] = self.mapy(n: scaledAmplitude, start1: 0.3, stop1: 0.9, start2: 0.0, stop2: 1.0)
                }
            }
        }

    }

    /// simple mapping function to scale a value to a different range
    func mapy(n:Double, start1:Double, stop1:Double, start2:Double, stop2:Double) -> Double {
        return ((n-start1)/(stop1-start1))*(stop2-start2)+start2;
    }
}
But unfortunately, the app crashes on launch, attempting to start the engine.
Matt54 / SwiftUI-AudioKit-Visualizer

It's not working anymore! #5
