[FIX] website: fix full height snippet option when a modal is open

Steps to reproduce the bug:

- In Website edit mode.
- Drag and drop a "Cover" snippet into an empty page.
- Sets the "Height" option of this snippet to "100%".
- Drag and drop a "Media List" snippet into the page.
- Drag and drop a "Popup" snippet into the page.
- Save the page.
- Scroll quickly the page to the bottom before the popup appears.
- When the popup is open, resize the window to trigger a "resize" event.
- Close the popup.
- Scroll the page to the top.
- Bug: the height of the "Cover" snippet is a way too high.

This bug occurred because the height of the snippet with the "Height:
100%" option enabled is calculated based on the scrollable element it is
in (since this commit [1]). However, when a popup is opened, the
detected scrollable element was incorrect due to the "overflow: hidden"
rule added to "#wrapwrap" by the "modal-open" class on the <body>.

[1]: https://github.com/odoo/odoo/commit/b371cb42cb67115692464c102813b7ebd54785d9

opw-3643498

closes odoo/odoo#152402

X-original-commit: 35b3f676820f7a19e842b3403a5ebcf956714a70
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>
Signed-off-by: Benjamin Vray (bvr) <bvr@odoo.com>

addons/website/static/src/js/content/snippets.animation.js

@@ -1142,7 +1142,16 @@ registry.FullScreenHeight = publicWidget.Widget.extend({
         // Doing it that way allows to considerer fixed headers, hidden headers,
         // connected users, ...
         const firstContentEl = $('#wrapwrap > main > :first-child')[0]; // first child to consider the padding-top of main
+        // When a modal is open, we remove the "modal-open" class from the body.
+        // This is because this class sets "#wrapwrap" and "<body>" to
+        // "overflow: hidden," preventing the "closestScrollable" function from
+        // correctly recognizing the scrollable element closest to the element
+        // for which the height needs to be calculated. Without this, the
+        // "mainTopPos" variable would be incorrect.
+        const modalOpen = document.body.classList.contains("modal-open");
+        document.body.classList.remove("modal-open");
         const mainTopPos = firstContentEl.getBoundingClientRect().top + $(firstContentEl.parentNode).closestScrollable()[0].scrollTop;
+        document.body.classList.toggle("modal-open", modalOpen);
         return (windowHeight - mainTopPos);
     },
 });