issue with deleting form fields

Dear Support,

I want to scan the document and obtain all the adobe fillable fields (step 1), get their information and then remove them from the document (step 2) as seen below:

            //Step 1: Get all Adobe fields.
            Aspose.Pdf.Facades.Form form = new Aspose.Pdf.Facades.Form(copy_filename);

            //get all field names
            String[] allfields = form.FieldNames;
            Aspose.Pdf.Facades.FormFieldFacade fieldfacade = null;

            foreach (string mFieldName in allfields)
            {

                fieldfacade = form.GetFieldFacade(mFieldName);
              
                //Step 2: remove the Adobe fields.
                Aspose.Pdf.Facades.FormEditor formEditor = new Aspose.Pdf.Facades.FormEditor();
                formEditor.BindPdf(root + "/" + id + ".pdf");

                //delete field

                formEditor.RemoveField(mFieldName);
                formEditor.Save(filename); // save this to filename which is original.
                formEditor.Close();
            }

For the attached example documents, Paycheck.pdf seems to work fine with no problem or errors.

However, for the document AdobeApplication2014.pdf, I get an error at the following line:
 formEditor.RemoveField(mFieldName);

Message:
{"Message":"An error has occurred.","ExceptionMessage":"Object reference not set to an instance of an object.","ExceptionType":"System.NullReferenceException","StackTrace":"   at Aspose.Pdf.InteractiveFeatures.Forms.Field.\u0019\u0003(String )\r\n   at Aspose.Pdf.InteractiveFeatures.Forms.Form.\u0019\u0003(String )\r\n   at Aspose.Pdf.InteractiveFeatures.Forms.Form.Delete(String fieldName)\r\n   at Aspose.Pdf.InteractiveFeatures.Forms.Form.Delete(Field field)\r\n   at Aspose.Pdf.Facades.FormEditor.RemoveField(String fieldName)\r\n   at FieldGeneratorSystem.Controllers.DocumentController.GetAdobeFields() in c:\\Users\\Jonathan\\Documents\\GitHub\\SNAsposeNet\\FieldGeneratorSystem\\Controllers\\DocumentController.cs:line 203\r\n   at FieldGeneratorSystem.Controllers.DocumentController.GetDocumentFields(String filename, String userDefinedTags) in c:\\Users\\Jonathan\\Documents\\GitHub\\SNAsposeNet\\FieldGeneratorSystem\\Controllers\\DocumentController.cs:line 132\r\n   at FieldGeneratorSystem.Controllers.DocumentController.<>c__DisplayClass37.<PostDocument>b__36(Task`1 t) in c:\\Users\\Jonathan\\Documents\\GitHub\\SNAsposeNet\\FieldGeneratorSystem\\Controllers\\DocumentController.cs:line 348\r\n   at System.Threading.Tasks.ContinuationResultTaskFromResultTask`2.InnerInvoke()\r\n   at System.Threading.Tasks.Task.Execute()"}

What could be the problem with the second document? Is the formEditor null? If yes, why? How can I solve it?

Thank you,
Sireesha