Modal is rendered empty on the first open

[mvorisek]

Discovered on atk4/login, I think it is atk4/ui issue.

Steps to reproduce:

1. checkout Adjust to latest atk4/data login#77
2. composer install
3. setup demo database using atk4/login/demos/admin-setup.php
4. open atk4/login/demos/admin-roles.php
5. click:
   
6. click:
   
7. empty modal is shown:
   

Notes:
a) after the steps above, when you click "x" to close the modal step, it returns to the previous modal, repeating the step 6 then opens the modal correctly
b) issue is repeatable, but only once per unknown reset conditions - I use Firefox, repeatable when browser is clearly started and step 6 is clicked the first time per row record

I think there is some race condition when initializing the model step in JS. I have verified, the data are rendered from the server correctly, but not shown.