core-bundle/src/Resources/contao/widgets/InputUnit.php
protected function isSelected($arrOption)
	{
		if (empty($this->varValue) && empty($_POST) && $arrOption['default'])
		{
			return $this->optionSelected(1, 1);
		}

		if (empty($this->varValue) || !\is_array($this->varValue))
		{
			return '';
		}

		return $this->optionSelected($arrOption['value'], $this->varValue['unit']);
	}
protected function isSelected($arrOption)
	{
		if (empty($this->varValue) && empty($_POST) && $arrOption['default'])
		{
			return $this->optionSelected(1, 1);
		}

		if (empty($this->varValue) || !\is_array($this->varValue))
		{
			return '';
		}

		return $this->optionSelected($arrOption['value'], $this->varValue['unit']);
	}
Only check against the unit values (see #7246)

@param array $arrOption The options array

@return string The "selected" attribute or an empty string