update AD from CSV skipping Blank " " fields

How  do I get this to use the  Set-ADUser -Replace @params 

I get this error message as DepartmentNumber  is not a normal  property, and in my last script i had to use the set-aduser -replace

Otherwise is looks like this script is actually doing the goal of updating AD properties from the spreadsheet and it doesnt care i have blank fields .

here is my headers

City               postalcode        OfficePhone             DepartmentNumber

Rockford          61008          222-222-5555            D2255

Set-ADUser : A parameter cannot be found that matches parameter name 'DepartmentNumber'.
At C:\Users\gdrews\desktop\Update-ADattributes\adup5.ps1:18 char:15
+     Set-ADUser <<<<  @params
    + CategoryInfo          : InvalidArgument: (:) [Set-ADUser], ParameterBindingException
    + FullyQualifiedErrorId : NamedParameterNotFound,Microsoft.ActiveDirectory.Management.Commands.SetADUser

$properties = @(
    'city',
    'postalcode',
    'OfficePhone'
    'DepartmentNumber'
        )

Import-Csv c:\temp\users.csv |
ForEach-Object {
    $params =  @{}
    foreach ($property in $properties)
     {
       if ($_.$property)
         { $params.$property = $_.$property }
     }

    get-ADUser -LDAPFilter "(samaccountname=$($_.samaccountname))" |
    Set-ADUser @params
}