Crash in Generator::method_next when creating new properties on Generator

import QtQuick 2.15

Rectangle {
   id: fileContainer
   property real a: 42 
   property real b: 0

   function f(myfunc) {
      let gen = myfunc();
      gen["u"] = 0
      console.log(gen.next().value)
   }

   function refreshA() {
      f(function*() { b= 12; return a });
   }

   TapHandler {
      onTapped:() => {fileContainer.refreshA(); console.log(fileContainer.b)}
   }
}