Specifications, info disappears when selecting variants

if(!empty($this->fields)) {
?>
	<div id="hikashop_product_custom_info_<?php echo $variant_name; ?>" style="display:none;">
		<h4><?php echo JText::_('SPECIFICATIONS'); ?></h4>
		<table class="hikashop_product_custom_info_<?php echo $variant_name; ?>">
<?php

			$this->fieldsClass->prefix = '';
			foreach($this->fields as $fieldName => $oneExtraField) {
				if(empty($variant->$fieldName) && !empty($this->element->main->$fieldName)) {
					$variant->$fieldName = $this->element->main->$fieldName;
				}
				if(!empty($variant->$fieldName))
					$variant->$fieldName = trim($variant->$fieldName);

				if(!empty($variant->$fieldName) || (isset($variant->$fieldName) && $variant->$fieldName === '0')) {
?>
			<tr class="hikashop_product_custom_<?php echo $oneExtraField->field_namekey; ?>_line">
				<td class="key">
					<span id="hikashop_product_custom_name_<?php echo $oneExtraField->field_id; ?>_<?php echo $variant_name; ?>" class="hikashop_product_custom_name"><?php echo $this->fieldsClass->getFieldName($oneExtraField); ?></span>
				</td>
				<td>
					<span id="hikashop_product_custom_value_<?php echo $oneExtraField->field_id; ?>_<?php echo $variant_name; ?>" class="hikashop_product_custom_value"><?php echo $this->fieldsClass->show($oneExtraField,$variant->$fieldName); ?></span>
				</td>
			</tr>
<?php
				}
			}
?>
		</table>
	</div>
<?php
		}