check only for undefined description

Author: bourgeoa

sourcePane.js

@@ -230,7 +230,7 @@ module.exports = {
         .then(function (response) {
           if (!happy(response, 'GET')) return
           const desc = response.responseText
-          if (!desc) { // Defensive https://github.com/linkeddata/rdflib.js/issues/506
+          if (desc === undefined) { // Defensive https://github.com/linkeddata/rdflib.js/issues/506
             const msg = 'source pane: No text in response object!!'
             statusRow.appendChild(UI.widgets.errorMessageBlock(dom, msg))
             return // Never mis-represent the contents of the file.