FaceMask Touch Textures

Hello,

I'm having trouble with the code provided by  https://lensstudio.zendesk.com/hc/en-us/community/posts/115020451643-Make-Things-Change-on-Tap 

Instead of sprite I want to change the textures/images of a facemask, ideally I want to change the lips and eyelashes to a different texture. 

Here is the code so far, but I get a error. 

16:49:17 Error: Argument -1: Value is not a native object
at [anon] () native strict preventsyield
at [anon] (FaceChangeScript:10) preventsyield

// -----JS CODE-----

// @input Component.FaceMaskVisual faceMask

// @input Asset.Texture[] textures







// Our starting texture index

var currentItemIndex = 0;




// Assign the initial texture to our sprite

script.faceMask.mainPass.baseTex = script.textures[currentItemIndex]




// Define what happens when you tap.

function changeTexture () {




// Increment the current item index

currentItemIndex += 1;




// We need the current item index to wrap around

// once it's higher than the number of items we have.

currentItemIndex = currentItemIndex % script.textures.length;




// Change the sprite's texture

script.faceMask.mainPass.baseTex = script.textures[currentItemIndex];

}




// Bind the function to the touch event.

var touchEvent = script.createEvent("TapEvent");

touchEvent.bind(changeTexture);

 Thanks,