Rule description and descriptionHtml are incorrectly assertNonNull().

[MrTommyPickles]

In old Reddit it is possible to create rules without descriptions. However, the Rule class constructor asserts description and descriptionHtml as non-null. This causes calls to subreddit.getRules() to fail for subreddits with rules lacking descriptions.

        assertNonNull(shortName, 'Subreddit rule is missing shortName');
        assertNonNull(description, 'Subreddit rule is missing description');
        assertNonNull(priority, 'Subreddit rule is missing priority');
        assertNonNull(createdUtc, 'Subreddit rule is missing createdUtc');
        assertNonNull(descriptionHtml, 'Subreddit rule is missing descriptionHtml');