文件夹权限的Powershell Null值

Question

我有以下Powershell代码：

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$Rights = "FullControl" #Comma seperated list, 2 rows, user and path.
$InheritSettings = "ContainerInherit, ObjectInherit" #Controls how permissions are inherited by children
$PropogationSettings = "None" #Usually set to none but can setup rules that only apply to children.
$RuleType = "Allow" #Allow or Deny.
$csv = Import-CSV "C:\scripts\test.csv" -delimiter ","
ForEach ($line in $csv) {
    $acl = Get-Acl $line.path
    $user = ('LSS\' + $line.user)

    $perm = $user, $Rights, $InheritSettings, $PropogationSettings, $RuleType
    $rule = New-Object -TypeName System.Security.AccessControl.FileSystemAccessRule -ArgumentList $perm
    $acl.SetAccessRule($rule)
    $acl | Set-Acl -Path $path
} 

我一直收到以下错误：

You cannot call a method on a null-valued expression.
At line:12 char:5
+     $acl.SetAccessRule($rule)
+     ~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

我已经检查了所有变量，但是仍然有这个问题。有人可以协助吗？