Error - "Invalid use of Null"

Any ideas on what may be causing this error?  If you need more info please let me know.
Thanks in advance.

I also attached a screen shot fron the debugger.

In the With cmd paragraph...
At the line...

intItemHeader = cmd.Parameters("iResult").Value

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The .Value contains a NULL which I suspect is where the invalid use of NULL is coming from.

Seems to cause this error...
Error - Error Pulling from pending, Please contact the system administrator! Invalid use of Null
Which is at PULL_ERR:

Code...

Public Function MoveItemPending(strItemCode As String, intItemPendingID As Long, intShipUnitsPack As Long, intInvUnitsPack As Long, strHItemCode As String, Optional intItemHeaderID As Long = 0) As Long
    Dim cmd As New ADODB.Command
    Dim intItemHeader As Long
    
    On Error GoTo PULL_ERR
    
    With cmd
        .Parameters.Append .CreateParameter("iresult", adInteger, adParamOutput, , 0)
        .Parameters.Append .CreateParameter("iresult_string", adChar, adParamOutput, 200, "")
        .Parameters.Append .CreateParameter("iuser_id", adInteger, adParamInputOutput, , userID)
        .Parameters.Append .CreateParameter("iID_Item_Pending", adInteger, adParamInputOutput, , intItemPendingID)
        .Parameters.Append .CreateParameter("iHeaderItem_Code", adChar, adParamInputOutput, 15, Left(Trim(strHItemCode), 15))
        .Parameters.Append .CreateParameter("iItem_Code", adChar, adParamInputOutput, 15, Left(Trim(strItemCode), 15))
        .Parameters.Append .CreateParameter("iReceived", adInteger, adParamOutput, , 0)
        .Parameters.Append .CreateParameter("iUnits_Pack", adInteger, adParamInputOutput, , intShipUnitsPack)
        .Parameters.Append .CreateParameter("iInv_Units_Pack", adInteger, adParamInputOutput, , intInvUnitsPack)
        .Parameters.Append .CreateParameter("iAllocation_Code", adInteger, adParamInputOutput, , 59)
        .Parameters.Append .CreateParameter("iID_Item_Header", adInteger, adParamInputOutput, , intItemHeaderID)
    End With
    
    SQLStoredProc strDSN, "spITS_MovePendingItem", cmd
    intItemHeader = cmd.Parameters("iResult").Value
    
    'change to put hook in so that it ask to open up item maintenance at this point
    If cmd.Parameters("iResult").Value > 0 Then
        If MsgBox(Trim(cmd.Parameters("iResult_string").Value) & Chr(13) & "Do you want to Modify this Item Now?", vbYesNo) = vbYes Then
            EditItemHeader intItemHeader
        End If
        
        'return Value
        MoveItemPending = intItemHeader
    Else
        MsgBox Trim(cmd.Parameters("iResult_string").Value), vbExclamation
        MoveItemPending = 0
    End If
    Exit Function
PULL_ERR:
    MsgBox "Error Pulling from pending, Please contact the system administrator!" & Chr(13) & Err.Description, vbExclamation
    MoveItemPending = 0
End Function

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2808---code-screen-shot.JPG