Unable to place OUTPUTs

[itxpert720]

Hi, I downloaded last sources, installed Unity 2019.4.32f1 Branch 2019.4/staging and running on Windows 7.

When I try to put an output on right side nothing happens and in console log I find this error :

NullReferenceException: Object reference not set to an instance of an object
ChipInterfaceEditor.HidePreviews () (at Assets/Scripts/Interaction/ChipInterfaceEditor.cs:250)
ChipInterfaceEditor.HandleInput () (at Assets/Scripts/Interaction/ChipInterfaceEditor.cs:152)
ChipInterfaceEditor.OrderedUpdate () (at Assets/Scripts/Interaction/ChipInterfaceEditor.cs:90)
ChipEditor.LateUpdate () (at Assets/Scripts/Graphics/ChipEditor.cs:35)

It seams coming from this : 
	void HidePreviews () {
		for (int i = 0; i < previewSignals.Length; i++) {
			previewSignals[i].gameObject.SetActive (false);
		}
	}

but I can't figure out why previewSignals[i].gameObject.SetActive (false) fails...

Error count increases all time from first time it appears, even if I do nothing. Thank you for your extraordinary work in every video.