<div id="filtr" class="textwidget">
      <?php if (is_home()): ?>
<?php echo wp_list_categories("orderby=name&title_li&show_count=0&hide_empty=0&hierarchical=1&depth=1"); ?>
<?php endif; ?>

<?php if (is_category('')): ?>
<?php $args = array(
    'orderby'            => 'name',
    'title_li'           => __( '' ),
    'show_count'         => 0,
    'hide_empty'         => 0,
    'child_of'           => $cat,
    'depth'              => 1,
); ?>
<?php echo wp_list_categories($args) ?>                          
<?php endif; ?>

      </div>