UserField::isValueEmpty

public function isValueEmpty($fieldValue): bool
{
	if (is_array ($fieldValue) && $this->isMultiple())
	{
		foreach ($fieldValue as $singleValue)
		{
			if (!$this->isValueEmpty($singleValue))
			{
				return false;
			}
		}

		return true;
	}

	// Interpret bool 'false' as non-empty for boolean type
	if ($this->isBaseTypeBoolean() && (bool)$fieldValue === false)
	{
		return false;
	}

	if (
		$this->isBaseTypeNumerical()
		&& ($fieldValue === 0 || $fieldValue === 0.0 || $fieldValue === "0" || $fieldValue === "0.0" || $fieldValue === "0,0")
	)
	{
		return false;
	}

	return empty($fieldValue);
}