Correctly display error when HTTP File Upload isn’t supported by the server.

dist/converse.js

@@ -70983,8 +70983,17 @@ _converse_core__WEBPACK_IMPORTED_MODULE_2__["default"].plugins.add('converse-cha
 
       async sendFiles(files) {
         const result = await _converse.api.disco.supports(Strophe.NS.HTTPUPLOAD, _converse.domain),
-              item = result.pop(),
-              data = item.dataforms.where({
+              item = result.pop();
+
+        if (!item) {
+          this.messages.create({
+            'message': __("Sorry, looks like file upload is not supported by your server."),
+            'type': 'error'
+          });
+          return;
+        }
+
+        const data = item.dataforms.where({
           'FORM_TYPE': {
             'value': Strophe.NS.HTTPUPLOAD,
             'type': "hidden"

src/headless/converse-chatboxes.js

@@ -418,8 +418,17 @@ converse.plugins.add('converse-chatboxes', {
 
             async sendFiles (files) {
                 const result = await _converse.api.disco.supports(Strophe.NS.HTTPUPLOAD, _converse.domain),
-                      item = result.pop(),
-                      data = item.dataforms.where({'FORM_TYPE': {'value': Strophe.NS.HTTPUPLOAD, 'type': "hidden"}}).pop(),
+                      item = result.pop();
+
+                if (!item) {
+                    this.messages.create({
+                        'message': __("Sorry, looks like file upload is not supported by your server."),
+                        'type': 'error'
+                    });
+                    return;
+                }
+
+                const data = item.dataforms.where({'FORM_TYPE': {'value': Strophe.NS.HTTPUPLOAD, 'type': "hidden"}}).pop(),
                       max_file_size = window.parseInt(_.get(data, 'attributes.max-file-size.value')),
                       slot_request_url = _.get(item, 'id');