core-bundle/src/Resources/contao/dca/tl_content.php
public function deleteElement($row, $href, $label, $title, $icon, $attributes)
	{
		$objElement = $this->Database->prepare("SELECT id FROM tl_content WHERE cteAlias=? AND type='alias'")
									 ->limit(1)
									 ->execute($row['id']);

		return $objElement->numRows ? Contao\Image::getHtml(preg_replace('/\.svg$/i', '_.svg', $icon)) . ' ' : '<a href="'.$this->addToUrl($href.'&amp;id='.$row['id']).'" title="'.Contao\StringUtil::specialchars($title).'"'.$attributes.'>'.Contao\Image::getHtml($icon, $label).'</a> ';
	}
public function deleteElement($row, $href, $label, $title, $icon, $attributes)
	{
		$objElement = $this->Database->prepare("SELECT id FROM tl_content WHERE cteAlias=? AND type='alias'")
									 ->limit(1)
									 ->execute($row['id']);

		return $objElement->numRows ? Contao\Image::getHtml(preg_replace('/\.svg$/i', '_.svg', $icon)) . ' ' : '<a href="'.$this->addToUrl($href.'&amp;id='.$row['id']).'" title="'.Contao\StringUtil::specialchars($title).'"'.$attributes.'>'.Contao\Image::getHtml($icon, $label).'</a> ';
	}
Return the delete content element button

@param array  $row
@param string $href
@param string $label
@param string $title
@param string $icon
@param string $attributes

@return string