Possible ordering bug

[Gary Ross]

When I repeat ordering I get an error message:
local.ERROR: Order direction must be "asc" or "desc".
The relevant file is
vendor/lifeonscreen/nova-sort-relations/src/SortRelations.php(64).

I think that the $direction variable can be empty which leads to the error message. It tends to happen on the 2nd click. My guess is that Nova sends an empty string on 'asc' (default) ordering and this leads to the issue. I have added a line that gives a simple fix

foreach ($orderings as $column => $direction) {
            $direction = $direction ?: 'asc';       // add this line
            if (array_key_exists($column, $sortRelations)) {
                $query = self::applyRelationOrderings($column, $direction, $query);
            } else {
                $query->orderBy($column, $direction);
            }
        }