In both of your initial screenshots with the line errors, I’m not seeing how the product is even getting there.
I would console.log(product) and see if you even have an object.
IN the first one, I don’t see where you pass product to that function
And in the second (line 123) again, I don’t see how product gets there so it may not be that the _id is null, it may be that you don’t have anythign there at all. Not sure, but I would suggest debugging at the level of the product object at each place you use it