i am trying to run the powershell script to get disk report for servers from text file but getting error

$  DiskSizeReport = @() $  servers = get-content "D:\Testing\Serverlist.txt" foreach ($  server in $  servers) { write-host "Executing query against server: " $  server $  Disks = Get-WmiObject win32_logicaldisk -computername $  server -Filter "Drivetype=3" -ErrorAction SilentlyContinue | Select-Object @{Label = "Server Name";Expression = {$  _.SystemName}}, @{Label = "Drive Letter";Expression = {$  _.DeviceID}},@{Label = "Total Capacity (GB)";Expression = {"{0:N1}" -f( $  _.Size / 1GB)}}, @{Label = "Used Space (GB)";Expression = {(Round($  _.Size /1GB,2)) - (Round($  _.FreeSpace /1GB,2))}}, @{Label = "Free Space (GB)";Expression = {"{0:N1}" -f( $  _.Freespace / 1GB ) }},@{Label = "Free Space (%)"; Expression = {"{0:P0}" -f ($  _.freespace/$  _.size) }} $  DiskSizeReport += $  Disks }    # Output to CSV   write-host "Saving Query Results in CSV format..." $  results | export-csv  "D:\Testing\Diskreport.csv"   -NoTypeInformation 

The below error I am getting

Get-WmiObject : Cannot validate argument on parameter ‘ComputerName’. The argument is null or empty. Provide an argument that is not null or empty, and then try the command again.
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