Use Powershell to Set DNS servers unless already null

I found a handy PowerShell script that will change the DNS servers to specified values. I'll paste it below. However, it is too efficient. A number of my servers use multiple NICs for iSCSI and have, by intent, no DNS addresses in their IP4 configuration. Is there a way to modify this script so it acts only on adapters which currently have a value set for the DNS resolver?

$servers = get-content "c:\scripts\computers.txt"
#$servers = "SERVERA","SERVERB","CLIENT1"
get-credential 
foreach($server in $servers) {
Write-Host "Connect to $server..."
$nics = Get-WmiObject Win32_NetworkAdapterConfiguration -ComputerName $server -ErrorAction Inquire | Where{$_.IPEnabled -eq "TRUE"}
$newDNS = "10.241.0.54","10.253.63.102"
 
foreach($nic in $nics) {
Write-Host "`tExisting DNS Servers " $nic.DNSServerSearchOrder
$x = $nic.SetDNSServerSearchOrder($newDNS)
 
if($x.ReturnValue -eq 0) {
Write-Host "`tSuccessfully Changed DNS Servers on " $server
} else {
Write-Host "`tFailed to Change DNS Servers on " $server
}
}
}

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