(bulma) CSS: fix content overflow in media object: Overflow was sometimes breaking design with media object. This was notably the case when viewing a list item with a long `<pre>` section, e.g. a ticket with a code pasted with long lines). This patch fixes it.

@media (min-width: 500px) {
    #main_area {
        background-image: var(--bg-img);
        background-repeat: no-repeat;
        background-size: cover;
    }
}