Scrape Sensor no state update

Configuration
1

Hi,
I made this sensor to get notified when the product is back in stock. I got the message when the product was briefly back in stock. My sensor value is now stuck at “add to cart”. This was the innerText of the dom element with .btn-shopping-cart. Why does it not change back to unknown or null or something? The Dom Element is not currently present on the website. Can it not handle the case of non existing elements?

- platform: scrape
  resource: <the shop url>
  name: <name>
  select: ".btn-shopping-cart"
  headers:
    User-Agent: Mozilla/5.0
2

Turns out, that the scrape sensor throws an error if the selector doesn’t match any dom element. Thus the value stayed on “add to cart”.
I changed the selector to ‘.product-description > *:last-child’ which matches the either the div with ‘out of stock’ or button with ‘add to cart’.
Imo that’s not a good behaviour. If the selector doesn’t match it should return a falsy value and not an error.