В файле design\user\default\blocks\new_category_tree.tpl.html
меняем
{if $smarty.const.CONF_SHOW_COUNTPROD eq 1} {$big_categories_tree[h].products_count}{/if}{if $smarty.const.CONF_MOD_REWRITE eq 1}category_{$big_categories_tree[h].categoryID}.html{else}index.php?categoryID={$big_categories_tree[h].categoryID}{/if}
на
{if $big_categories_tree[h].subcount > 0}
{if $smarty.const.CONF_SHOW_COUNTPROD eq 1} {$big_categories_tree[h].products_count}{/if} 0}onclick="flip('{$big_categories_tree[h].categoryID}')" id="p_s_{$big_categories_tree[h].categoryID}"{/if}>{$big_categories_tree[h].name}
{else}
{if $smarty.const.CONF_SHOW_COUNTPROD eq 1} {$big_categories_tree[h].products_count}{/if}{if $smarty.const.CONF_MOD_REWRITE eq 1}category_{$big_categories_tree[h].categoryID}.html{else}index.php?categoryID={$big_categories_tree[h].categoryID}{/if}
{/if}