Checking if LocalDateTIme is null in a conditional

Here I have a function that formats a string to a LocalDateTime and returns it.

val dateSentFormatted = timeFormatted(record.data.dateTime);

private fun timeFormatted(dateEmailSent: String?): LocalDateTime {
    val formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd:HH:mm:ss");
    return LocalDateTime.parse(dateEmailSent, formatter);
}

My question is I wanted an if statement to run on it elsewhere in my file to check whether it's null as in:

if (!dateSentFormatted != null ) {

}

But it doesn't like that, how else can I check whether a variable of type LocalDateTime is empty in an if statement?