Powershell Script for adding CT fails

#FÜR ALLE WEBS aller SITECOL und Subweb

="http://aktiv/"

="Arbeitsbereich Excel"  #Excel  or Powerpoint

="Dokumente"

=Get-SPWebApplication-identity$WEB_APPLICATION_URL

($siteCollectionin$webApplication.Sites)

#Walk through each site in the site collection

ForEach($subSitein$siteCollection.AllWebs)

write-host"Checking site:"$subSite.URL

$update=$false

#Go through each document library in the site

$subSite.Lists|where{$_.Title -eq$lookForList-and$subSite.URL -match'sc002'}|ForEach-Object{

write-host"Checking list:"$_.Title

$_.ContentTypesEnabled=$true

$_.Update()

#Check to see if the library contains the content type specified

#at the start of the script

if(($_.ContentTypes|where{$_.Name-eq$lookForCT})-eq$null)

write-host"No content type exists with the name"$lookForCT"on list"$_.Title

$update=$true;

else

write-host"YES content type exists with the name"$lookForCT"on list"$_.Title

if($update) {

#Add site content types to the list

$ctToAdd=$subSite.RootWeb.ContentTypes[$lookForCT]

write-host"CT = "$ctToAdd.Name

#$ct = $_.ContentTypes.Add($ctToAdd)

$ct=$_.Lists[$lookForList].ContentTypes.Add($ctToAdd)

write-host"Content type"$ct.Name"added to site "$subSite.URL

#$_.Update()

.Dispose()

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HC