Trying to use remote variable in If-Condition within ScriptBlock using PowerShell - powershell-remoting

Question

I am trying to use below code to remove the groups from Active Directory. I am maintaining an input file for the list of servers. the input file is in the local machine and trying to use the content of the file inside the ScriptBlock using ($Using:variablename) after taking a remote session.
I am getting the content[file content] of the variable inside the ScriptBlock which is defined outside the ScriptBlock. The issue is the if condition [if($serverlist -ne $null)] is satisfying even if the variable is empty. The code is entering into if block even if the variable $serverlist is null, instead it has to take else block.
Could you please help me on this.
$adserver = Read-Host -Prompt "Please enter AD server details"
$adserver
$askcredential = $host.ui.PromptForCredential("Need credentials", "Please enter your user name and password.", "", "NetBiosUserName")
$credential = New-Object System.Management.Automation.PsCredential($askcredential.UserName,$askcredential.Password)
$session = New-PSSession -ComputerName "$adserver" -Credential $credential
#$command = (Get-ADForest).domains
$addomain = Read-Host -Prompt "Please enter the Domain"
$servers = Get-Content "D:\Bhargavi\Windows-Decommission\$addomain\servers.txt"
#Invoke-Command -ComputerName $adserver -Authentication Default -Credential $credential -ScriptBlock {
Invoke-Command -Session $session -ScriptBlock {
#$addomain = Read-Host -Prompt "Please enter the Domain"
#$servers = Get-Content "D:\Bhargavi\Windows-Decommission\$addomain\servers.txt"
#Param($domainname,$serverlist)
$serverlist = $Using:servers
$domainname = $Using:addomain
Write-Host "the list is $serverlist"
Write-Host "the domain is $domainname"
if($serverlist -ne $null)
{
Write-Host "Found the data in the input file. Proceeding to remove the groups."
foreach ($server in $serverlist)
{
write-host "Server Name is: $server"
$mgserver = "MG-$server"
$mggroup = Get-ADGroup -Filter { Name -like $mgserver }
$mggroup
if($mggroup -ne $null)
{
Get-ADGroup -Filter { Name -like $mgserver } #| Remove-ADGroup -Confirm:$False
$mggroupconfirm = Get-ADGroup -Filter { Name -like $mgserver }
if($mggroupconfirm -eq $null)
{
Write-Host "$mgserver is removed from $domainname"
#Set-Content -Path "D:\Bhargavi\Windows-Decommission\$domainname\servers.txt" -Value (get-content -Path "D:\Bhargavi\Windows-Decommission\$domainname\servers.txt" | Select-String -Pattern "$server" -NotMatch)
}
else
{
Write-Host "$mgserver is not removed. Please try again."
}
}
else{Write-Host "There is no group called $mgserver in $domainname domain "}
}
}
else
{
DO
{
$val = Read-Host -Prompt "Do you want to enter servername ? Enter yes or no"
if($val -eq "yes")
{
$entermgserver = Read-Host -Prompt "Please enter the server name"
$entermgserver
$mgserver = "MG-$entermgserver"
$mgserver
$mggroup = Get-ADGroup -Filter { Name -like $mgserver }
$mggroup
if($mggroup -ne $null)
{
#Write-Host "$mggroup is not null"
Get-ADGroup -Filter { Name -like $mgserver } #| Remove-ADGroup -Confirm:$False
$mggroupconfirm = Get-ADGroup -Filter { Name -like $mgserver }
if($mggroupconfirm -eq $null)
{
Write-Host "$mgserver is removed"
}
else
{
Write-Host "$mgserver is not removed. Please try again."
}
}
else{Write-Host "The is no group called $mgserver in $domainname domain"}
}
}until ($val -eq "no")
}
} ### End Script Block
Clear-Content "D:\Bhargavi\Windows-Decommission\$addomain\servers.txt"
Remove-PSSession -Session $session