Need help with my first error handler

I work for a small company and have been tasked with building a database application to help with some of our industry-specific tracking needs.  I am NOT a database developer or VB coder.  My experience is limited to industrial PLC programming and the occasional small Python script.  

The project includes a Form that executes an OnCurrent event which calls a Class Module (which I did not write the code for).  The purpose of the code is to acquire the Width and Height dimensions (in pixels) of an on-disk image file.  The code executes correctly if the record includes a valid image path.  However, if there is no valid path, I get the following error:
at this line of code in my Form:
Here is the code for the ImageDimensions class module:

Option Compare Database
Option Explicit

Private pPixelWidth As Long
Private pPixelHeight As Long
Private pImageFullPath As String

Public Property Get ImageFullPath() As String
  ImageFullPath = pImageFullPath
End Property
Public Property Let ImageFullPath(fullPath As String)
  pImageFullPath = fullPath
  Dim dimensionsText As String

  dimensionsText = GetImageDimensions(fullPath)
  pPixelWidth = Left$(dimensionsText, InStr(dimensionsText, ",") - 1)
  pPixelHeight = Mid$(dimensionsText, InStr(dimensionsText, ",") + 1)
End Property

Public Property Get PixelWidth() As Long
  PixelWidth = pPixelWidth
End Property
Private Property Let PixelWidth(value As Long)
  pPixelWidth = value
End Property

Public Property Get PixelHeight() As Long
  PixelHeight = pPixelHeight
End Property
Private Property Let PixelHeight(value As Long)
  pPixelHeight = value
End Property

Private Function GetImageDimensions(ByVal fullPath As String)
  Dim fileName As String
  Dim fileFolder As String
  fileName = FilenameFromPath(fullPath)
  fileFolder = FolderFromFilePath(fullPath)

  Dim objShell As Object
  Set objShell = CreateObject("Shell.Application")

  Dim targetFolder As Object
  Set targetFolder = objShell.Namespace(fileFolder & vbNullString)

  Dim objFolderItem As Object
    Set objFolderItem = targetFolder.ParseName(fileName)
  'Const IMAGE_DIMENSIONS As Long = 31
  Dim dimensionsPrep As String
  'dimensionsPrep = targetFolder.GetDetailsOf( _
  '  targetFolder.Items.Item(fileName & vbNullString), _
  '  IMAGE_DIMENSIONS)
    dimensionsPrep = objFolderItem.ExtendedProperty("Dimensions")
  dimensionsPrep = Replace(dimensionsPrep, " x ", ",")
  dimensionsPrep = Mid$(dimensionsPrep, 2, Len(dimensionsPrep) - 2)
  GetImageDimensions = dimensionsPrep
End Function

Private Function FolderFromFilePath(ByVal filePath As String) As String
  Dim filesystem As Object
  Set filesystem = CreateObject("Scripting.FileSystemObject")
  FolderFromFilePath = filesystem.GetParentFolderName(filePath)
End Function

Private Function FilenameFromPath(ByVal filePathAndName As String) As String
  Dim pathLength As Long
  Dim iString As String
  pathLength = Len(filePathAndName)
  iString = vbNullString

  Dim iCount As Long
  For iCount = pathLength To 1 Step -1
    If Mid$(filePathAndName, iCount, 1) = "\" Then
      FilenameFromPath = iString
      Exit Function
    End If
    iString = Mid$(filePathAndName, iCount, 1) & iString
  Next iCount

  FilenameFromPath = filePathAndName
End Function

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The following code executes at db start, via an AutoExec macro, and creates TempVars:

Public Function StartUp()
    Dim sPath                 As String

    sPath = Nz(DLookup("Contents", "GlobalVars", "Variable='ImagesPath'"))
    If Right(sPath, 1) <> "\" Then sPath = sPath & "\"
    TempVars.Add "ImagePath", sPath

End Function

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GlobalVars is a table that contains the image path record in the ImagesPath column.
ImageName is a text box on my form.