Script not working in Powershell?

Question

PowerShell

The script works only if the fields homephone and mobile have phones, but if at least one field is empty, then it does not work, can you somehow correct the regular expression or is it better to add if, else conditions?
Get-ADUser -SearchBase "DC=mydomain,DC=local" -Filter * -properties homephone, mobile | Foreach {
# ALL
$homephone = $_.homephone -replace "\D"
$mobile = $_.mobile -replace "\D"
# RU
$mobile = $mobile -replace '^8(\D{10})$ ','7$1'
$homephone = $homephone -replace '^8(\D{10})$','7$1'
Set-ADUser $_ -mobilephone $mobile -homephone $homephone
}

Answer 1

try -properties * instead of -properties homephone, mobile