[FIX] web_editor: properly toggle active link button

The link button was toggling its active state on every update of the
toolbar because we weren't passing the toggle function a boolean. and
if the element we were passing it was `undefined`, it triggered the
default behavior which is to just toggle. Instead we want it to be false
if the element is `undefined`.

X-original-commit: 7aecd36a169033a89defeb00ba0ae53cd64cdcd5
Part-of: odoo/odoo#86930