Emtpy basket - Error Message needed


I Use an Additional Text as Option for the Variant Dropdown
Like "Chose Variant"
Of Course when someone try to buy that item hell get no Result

The Problem is now that now noting is happening. The Popup Windows shows for a Sec Emtpy and Returns to the Product.

I want to intercept that “buy nothing” submit to make an error message.
Where can i intercept it?

I know i know i could do it directly at the submitbutton itself - but i dont like that idea.
i want to do the interception a bit later - where its normally processed
please just a hint :slight_smile: