Ladybird: Page Crashes Due to Unresolved CSS Variables in @keyframes Rule

[abdelfetah18]

When attempting to visit https://www.instagram.com/abdelfetah1337, the page crashes.

After some investigation, I've simplified the problem to the following code snippet:

<style>
    :root {
        --accent: #00f;
    }

    @keyframes myMove {
        0% {
            border-top: 2px solid var(--accent);
        }
    }

    div {
        animation: myMove 1s infinite;
    }
</style>
<div>hello world</div>

[AtkinsSJ]

cc @mattco98 @kalenikaliaksandr