Added barcode generatin

ref #19

src/asyncHelpers.ts

@@ -3,6 +3,7 @@ import bwipjs from "bwip-js";
 
 export const asyncHelpers = new AsyncHelpers();
 async function generateBarcode(str, options, emtpy, cb) {
+    if (str == null) { cb(null, "data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAADUlEQVR42mNk+P+/HgAFhAJ/wlseKgAAAABJRU5ErkJggg=="); return; }
     let res = await generateBase64Barcode(options.toString(), str.toString());
     cb(null, res);
 }
@@ -18,7 +19,7 @@ export async function generateBase64Barcode(type: string, content: string): Prom
         height: 10,
         width: 10,
         includetext: true,
-        textxalign: 'center',
+        textxalign: 'center'
     }
     if (type != "qrcode") {
         delete options.width;