Loot at the code:
url
could be "undefined"
string, not the undefined
global variable nor null
literal, so the condition will be true in this case, and the system will try to do an AJAX request with undefined URL.
The error is strongly related to another error: The template()
function in lib/web/mage/utils/template.js
returns «undefined» values as a string, not as the undefined
global variable nor null
literal, which lead to mistakes in the core code’s logical expressions