Exception error when getting master page in powershell

Question

I wanted to see which site collections in our 2010 environment are not following the rules and are deactivating the Master Page in the settings.

I have some powershell code that works just fine, and it returns back the correct information but I get a bunch of exception errors. Anybody have any suggestions on how what I might be doing wrong?

Error message:

Exception calling "GetFile" with "1" argument(s): "Value does not fall within the expected range." At line:13 char:35 + $MasterPage = $Web.GetFile <<<< ($Web.MasterUrl) + CategoryInfo : NotSpecified: (:) [], MethodInvocationException + FullyQualifiedErrorId : DotNetMethodException

Here is my powershell script that I am using:

    Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue


    #Get all site collections of provided web app

$SiteCollections = Get-SPWebApplication | Get-SPSite -Limit All

   #Loop through all site collections
   foreach($Site in $SiteCollections)
    {
       #Loop through all Sub Sites
       foreach($Web in $Site.AllWebs)
       {   
        #Get the Master Page
        $MasterPage = $Web.GetFile($Web.MasterUrl)
        if ($MasterPage.name -ne "corp.master")
             {
                     $MasterPage.Name  + " : " + $Web.Url 
             }
       }

    }

Thanks guys!

Answer 1

Why not just check the CustomMasterUrl and MasterUrl properties that are on the SPWeb object itself and bypass the slow and expensive GetFile() altogether?

        if ($Web.MasterUrl.EndsWith("corp.master") -eq $false)
           $Web.MasterUrl + " : " + $Web.Url     
        }