How to conditionally add data to a groq-query if the array is empty

"users" : *[_type=="user" && references(^._id)]  { 
    initial data goes here...
},
users.length === 0 => {
   new data goes here if we could not get any users 
}

`*[_type=="docs" && uuid == $uuid][0] {
  _id,
  "users" : *[_type=="user" && references(^._id)] {
    initial data... 
   },
 count(users) > 0 => { ...more data }
}