Hi,
There is already such code in product / listing.php:
echo '<div class="hk-well hika_no_products"><i class="fa fa-search"></i> ' . JText::_('HIKASHOP_NO_RESULT') . '</div>';
However, it is set to display only after you use a filter, not when there are no products in the category.
But you can change that.
For it to appear also when there are products in the category, you can change the line:
} elseif(( !$this->module || hikaInput::get()->getVar('hikashop_front_end_main',0) ) && ($ctrl == 'product' || $ctrl == 'category') && $task == 'listing' && !empty($this->filters) && is_array($this->filters) && count($this->filters) && !empty($this->filter_set)) {
to:
} elseif(( !$this->module || hikaInput::get()->getVar('hikashop_front_end_main',0) ) && ($ctrl == 'product' || $ctrl == 'category') && $task == 'listing') {