The error happens because the code in template.js is looking for header divs to process them. However, in modals these elements are not displayed by the template.

That's the wrong assumption, the script is not loaded for the modals if the correct entry point is set. In the core wherever there's a modal the iframe URL is always pointing to ?tmpl=component so that the modal will not load unneeded code:

Here's one example:

And the relative code that disables the script in the component.php entry point:

In short, this is not a core problem...

Thanks for your answer.

I understand what you're saying, however, the URL of the modal I'm pointing at also has &tmpl=component in it. Here is a screenshot of the content of the modal loaded directly :
https://i.imgur.com/AE8OzWo.png
You can see that the URL has the &tmpl=component parameter but there is the JS error on the template.js file in the console.

Nevertheless, the file media/templates/administrator/atum/js/template.js is still in the header.
And I don't know how that is possible nor what I should do or where to look to find what is doing that. Do you have an idea ?
I tried adding

	$wa = JFactory::getApplication()->getDocument()->getWebAssetManager();
	$wa->disableScript('template.atum');

to the view displaying the invoice modal in HikaShop, but it doesn't change anything, which is normal since the component.php file of the template is processed after the view file and already does it.

On another note, wouldn't adding the extra check in the javascript be a good practice in case something unexpected happens on the page and the HTML is not there ?

However, I think it would be better to modify the javascript of the template to check that the elements are there before processing them.

As you already know the fix, please make a PR

However, I think it would be better to modify the javascript of the template to check that the elements are there before processing them.

As you already know the fix, please make a PR

Well, I wanted to discuss if this was a good idea or not as I'm not familiar with atum or that javascript.

Some more of if() should not be bad :)

You can see that the URL has the &tmpl=component parameter but there is the JS error on the template.js file in the console.

if that’s the case then this is a bug in the atum template. In the component.php the template.js should be ignored

@hikashop-nicolas Ok the problem is on your side, the URL needs to be like:
http://host.local:8080/joomla-cms/administrator/index.php?option=com_hikashop&ctrl=order&task=invoice&tmpl=component&type=full&order_id=1
but it is like http://host.local:8080/joomla-cms/administrator/index.php?option=com_hikashop&ctrl=order&task=invoice&tmpl=component&type=full&order_id=1

the & parts are breaking the bank here

you should escape the url only if it’s going to be displayed in the browser, for php usage keep the non escaped

I guess this can be closed

The URL is not the problem. If you check my previous screenshot, the javascript error is there in the console even though the URL has & and not & in the address bar of the browser.
Are you saying you don't have the error on your end when you look at the invoice ?
In that case, it must mean that there is something else at play which ends up loading the template.js file for some reason on my end and not on yours.

But as Fedik said, I think it's a good idea to add some extra checks in the javascript of the template. I'll look at submitting a PR.

@hikashop-nicolas check your HTML of the iframe. Copy the URL to another browser tab and then edit it and replace the & with &

Fixing the template.js won't fix anything on your side as you're loading the complete backend (menu, top bar, etc)

The URL is not the problem. If you check my previous screenshot, the javascript error is there in the console even though the URL has & and not & in the address bar of the browser.

Pfff that's the URL of the top page I'm talking about the URL of the iframe Check my images, these are the URLs of the IFRAME, the first one is what your component produces (which is completely wrong) and the 2nd one is what would work...

Seriously there's nothing wrong with the core here, you're escaping the URL when you shouldn't, that's all

No, that's not the URL of the top page, it's the URL of the iframe that I had already openned in another tab.
Please look at my screenshot again: https://i.imgur.com/AE8OzWo.png
The screenshot is of the iframe that I openned in another tab. I did it like that especially to show you that the URL of the iframe is correct and I still have the js error.
If the parameters of the URL for the popup had amp; then the popup would display the dashboard of HikaShop with the Joomla menus and everything, like in your screenshot, with the URL with the amp;.
But as you can see if you look at the popup, it doesn't show the dashboard and the joomla menus in it, only the invoice.

Also if you check the HTML of the top page where the button is, the URL is correct, without the amp; , see here: https://i.imgur.com/h3hTCoT.png
So I'm not sure where you're getting the amp; in your URL from.

@hikashop-nicolas you can add some breakpoints both in the index.php and the component.php to debug this. I already told you what's failing and it's not component.php as that entry point DOES NOT LOAD the template.js...

Yes, I understood that, and I thank you for that explanation.

can this be closed then ? @hikashop-nicolas