TypeError: Cannot find function getSubject in object GmailThread. (line 28, file "dl")

pdftotext.js

// GLOBALS
//Array of file extension which you would like to extract to Drive
 var fileTypesToExtract = ['pdf'];
//Name of the folder in google drive in which files will be put
 var folderName = 'New Order pdfs';
//Name of the label which will be applied after processing the mail message
 var labelName = 'Orderdownloaded';

 function GmailToDrive(){
  //build query to search emails
  var query = '';
  //   filename:jpg OR filename:tif OR filename:png OR fileName:gif OR filename:bmp OR filename:pdf'; //'after:'+formattedDate+
  for(var i in fileTypesToExtract){
	query += (query == '' ?('filename:'+fileTypesToExtract[i]) : (' OR filename:'+fileTypesToExtract[i]));
  }
   query = 'label:inbox label:exam label:New_order -label:Orderdownloaded -label:ordertotext' + query;
  var threads = GmailApp.search(query);
  var label = getGmailLabel_(labelName);
 var deletelabel = getGmailLabel_('Exam'); 
  var parentFolder;
  if(threads.length > 0){
    parentFolder = getFolder_(folderName);
  }
  var root = DriveApp.getRootFolder();
  for(var i in threads){
    var mesgs = threads[i].getMessages();
//dhf
   var messageSubject = threads[i].getSubject();
   var messageDate = threads[i].getDate();
//dhf    
	for(var j in mesgs){
      //get attachments
      var attachments = mesgs[j].getAttachments();

      for(var k in attachments){
        var attachment = attachments[k];

        var isImageType = checkIfImage_(attachment);
    	if(!isImageType) continue;
        
        
        
        
    	var attachmentBlob = attachment.copyBlob();
//********************************************************************************************************************************************        
 
function pdfToText ( pdfFile, options ) {        
        
        // Start with a Blob object
  
 //  var blob = gmailAttachment.getAs(MimeType.PDF);
 
     var blob = attachment.copyBlob();
    
    // fileId will be the ID of a saved text file (default behavior):
    var fileId = pdfToText( blob );

    // filetext will contain text from pdf file, no residual files are saved:
    var filetext = pdfToText( blob, {keepTextfile: false} );

    // we can save other converted file types, too:
    var options = {
       keepPdf : false,            // Keep a copy of the original PDF file.
       keepGdoc : true,           // Keep a copy of the OCR Google Doc file.
       keepTextfile : true,       // Keep a copy of the text file. (default)
       path : "New Order pdfs" // Folder path to store file(s) in.
    }
    filetext = pdfToText( blob, options );
    
  /**
 * Convert pdf file (blob) to a text file on Drive, using built-in OCR.
 * By default, the text file will be placed in the root folder, with the same
 * name as source pdf (but extension 'txt'). Options:
 *   keepPdf (boolean, default false)     Keep a copy of the original PDF file.
 *   keepGdoc (boolean, default false)    Keep a copy of the OCR Google Doc file.
 *   keepTextfile (boolean, default true) Keep a copy of the text file.
 *   path (string, default blank)         Folder path to store file(s) in.
 *   ocrLanguage (ISO 639-1 code)         Default 'en'.
 *   textResult (boolean, default false)  If true and keepTextfile true, return
 *                                        string of text content. If keepTextfile
 *                                        is false, text content is returned without
 *                                        regard to this option. Otherwise, return
 *                                        id of textfile.
 *
 * @param {blob}   pdfFile    Blob containing pdf file
 * @param {object} options    (Optional) Object specifying handling details
 *
 * @returns {string}          id of text file (default) or text content
 */
  

  // Ensure Advanced Drive Service is enabled
  try {
    Drive.Files.list();
  }
  catch (e) {
    throw new Error( "To use pdfToText(), first enable 'Drive API' in Resources > Advanced Google Services." );
  }
  
  // Set default options
  options = options || {};
  options.keepTextfile = options.hasOwnProperty("keepTextfile") ? options.keepTextfile : true;
  
  // Prepare resource object for file creation
  var parents = [];
  if (options.path) {
    parents.push( getDriveFolderFromPath (options.path) );
  }
  var pdfName = pdfFile.getName();
  var resource = {
    title: pdfName,
    mimeType: pdfFile.getContentType(),
    parents: parents
  };
  
  // Save PDF to Drive, if requested
  if (options.keepPdf) {
    var file = Drive.Files.insert(resource, pdfFile);
    
  }
  
  // Save PDF as GDOC
  resource.title = pdfName.replace(/pdf$/, 'gdoc');
  var insertOpts = {
    ocr: true,
    ocrLanguage: options.ocrLanguage || 'en'
  }
  var gdocFile = Drive.Files.insert(resource, pdfFile, insertOpts);
  
  // Get text from GDOC  
  var gdocDoc = DocumentApp.openById(gdocFile.id);
  var text = gdocDoc.getBody().getText();
  
  // We're done using the Gdoc. Unless requested to keepGdoc, delete it.
  if (!options.keepGdoc) {
    Drive.Files.remove(gdocFile.id);
  }
  
  // Save text file, if requested
  if (options.keepTextfile) {
    resource.title = pdfName.replace(/pdf$/, 'txt');
    resource.mimeType = MimeType.PLAIN_TEXT;

    var textBlob = Utilities.newBlob(text, MimeType.PLAIN_TEXT, resource.title);
    var textFile = Drive.Files.insert(resource, textBlob);
  }
  
  // Return result of conversion
  if (!options.keepTextfile || options.textResult) {
    return text;
  }
  else {
    return textFile.id
  }
}

// Helper utility from http://ramblings.mcpher.com/Home/excelquirks/gooscript/driveapppathfolder
function getDriveFolderFromPath (path) {
  return (path || "/").split("/").reduce ( function(prev,current) {
    if (prev && current) {
      var fldrs = prev.getFoldersByName(current);
      return fldrs.hasNext() ? fldrs.next() : null;
    }
    else { 
      return current ? null : prev; 
    }
  },DriveApp.getRootFolder()); 
}
      
        
//********************************************************************************************************************************************        
        var file = DriveApp.createFile(attachmentBlob);
        parentFolder.addFile(file);
        root.removeFile(file);


      }
    }
	threads[i].addLabel(label);
    threads[i].removeLabel(deletelabel);
    
//dhf
    
     var ss = SpreadsheetApp.getActiveSheet();

//This appends the text of the pdf doc to the gsheet    
     ss.appendRow([messageDate, messageSubject, filetext])       
    
//dhf   

  }


//This function will get the parent folder in Google drive
function getFolder_(folderName){
  var folder;
  var fi = DriveApp.getFoldersByName(folderName);
  if(fi.hasNext()){
    folder = fi.next();
  }
  else{
    folder = DriveApp.createFolder(folderName);
  }
  return folder;
}

//getDate n days back
// n must be integer

function getDateNDaysBack_(n){
  n = parseInt(n);
  var today = new Date();
  var dateNDaysBack = new Date(today.valueOf() - n*24*60*60*1000);
  return dateNDaysBack;
}

function getGmailLabel_(name){
  var label = GmailApp.getUserLabelByName(name);
  if(label == null){
	label = GmailApp.createLabel(name);

  }
  return label;
}

//this function will check for filextension type.
// and return boolean

function checkIfImage_(attachment){
  var fileName = attachment.getName();
  var temp = fileName.split('.');
  var fileExtension = temp[temp.length-1].toLowerCase();
  if(fileTypesToExtract.indexOf(fileExtension) != -1) return true;
  else return false;
}}

Looking for some help on a script that I can't seem to figure out. It is a combination of this script:
https://stackoverflow.com/questions/26613809/get-pdf-attachments-from-gmail-as-text (thanks to the orginal author)
AND this one:
https://gist.github.com/Carolusian/9021828f284b31e1440c (thanks to the orginal author)
However, when I tried to combine the two I couldn't figure out how to get the subject of the email to pass through to the google sheet. Any help is much appreciated.