Empty string for Sid when using SPFile.CheckedOutByUser Sid Property

Hello,

Recently upgraded from 2010 to 2013 and now i'm having issues with this Infopath form. When debugging, file.CheckedOutByUser.Sid.ToString() return an empty string.

I've also check using 

PS C:\Users\FTAO> $web =Get-SPWeb http://site
PS C:\Users\FTAO> $web.SiteUsers["domain\FTAO"]

and I see Sid is being populated correctly.

I am not sure if I did something wrong during the upgrade process or if I am looking at the wrong place. Any insight on this is appreciated.

Dim file As SPFormFile = GetFile(FormUniqueID.Value)
If file.CheckOutType = SPFile.SPCheckOutType.None Then
	'***Tie in Security***
	If CurrentUserFormWriteAccess.Value = 1 Then
		CheckOutStatusText.SetValue("This Form is not checked out.")
		CanUserCheckOut.SetValue(1)
		CanUserCheckIn.SetValue(0)
	End If
ElseIf file.CheckOutType <> SPFile.SPCheckOutType.None Then
	CanUserCheckOut.SetValue(0)
	Dim filecheckoutuser As String = file.CheckedOutByUser.Sid.ToString()

	Dim filecheckoutdatetime As DateTime = file.CheckedOutDate
	If filecheckoutuser = CurrentUserSID.Value.ToString() Then
		CheckOutStatusText.SetValue("This Form is checked out to you. Checkout Date/Time: " & filecheckoutdatetime.AddHours(-5) & ".")
		CanUserCheckIn.SetValue(1)
	Else
		CheckOutStatusText.SetValue("This Form is checked out by " & file.CheckedOutByUser.Name.ToString() & ". Checkout Date/Time: " & filecheckoutdatetime.AddHours(-5) & ".")
	End If

End If

Update: Resolved the issue by using Victoria workaround.

Replaced

Dim filecheckoutuser As String = file.CheckedOutByUser.Sid.ToString()

with

Dim userLogin As String = file.CheckedOutByUser.LoginName.Substring(7)
Dim filecheckoutuser As String = SPContext.Current.Web.AllUsers(userLogin).Sid