(Swift) Initializer for conditional binding must have Optional type, not 'AVAudioInputNode' : <p>I am trying to create a speech to text function and I am getting the error:</p>

<p><code>Initializer for conditional binding must have Optional type, not 'AVAudioInputNode'</code></p>

<pre><code>guard let inputNode = audioEngine.inputNode else {
        fatalError("Audio engine has no input node")
    }
</code></pre>
