Interfaces/ZUGFeRD: check if any extension exists

Interfaces/ZUGFeRDInterface/PDFEmbeds.vb

@@ -165,7 +165,14 @@ Public Class PDFEmbeds
                     If GDPicturePDF.GetStat() = GdPictureStatus.OK Then
                         Logger.Debug("Extracting embedded file [{0}]", oFileName)
 
-                        Dim oExtension = New FileInfo(oFileName).Extension.ToUpper.Substring(1)
+                        Dim oFileInfo = New FileInfo(oFileName)
+                        Dim oExtension As String = oFileInfo.Extension
+
+                        If String.IsNullOrWhiteSpace(oExtension) Then
+                            Logger.Error("The embedded file [{0}] does not have any extension. Skipping.")
+                            Continue For
+                        End If
+
                         If pExtensions.Contains(oExtension) Then
                             Dim oFileSize As Integer = GDPicturePDF.GetEmbeddedFileSize(oIndex)