Fixes sitemap image errors

closes #4591

- switches to using author cover image
- adds a protocol of http if using a protocol relative url

core/server/data/sitemap/user-generator.js

@@ -1,8 +1,9 @@
-var _ = require('lodash'),
-    path = require('path'),
-    api = require('../../api'),
-    BaseMapGenerator = require('./base-generator'),
-    config = require('../../config');
+var _                   = require('lodash'),
+    path                = require('path'),
+    api                 = require('../../api'),
+    BaseMapGenerator    = require('./base-generator'),
+    validator           = require('validator'),
+    config              = require('../../config');
 
 // A class responsible for generating a sitemap from posts and keeping it updated
 function UserMapGenerator(opts) {
@@ -45,18 +46,21 @@ _.extend(UserMapGenerator.prototype, {
             imageEl;
 
         // Check for image and add it
-        if (datum.image) {
+        if (datum.cover) {
             // Grab the image url
-            imageUrl = this.getUrlForImage(datum.image);
-            // Create the weird xml node syntax structure that is expected
-            imageEl = [
-                {'image:loc': imageUrl},
-                {'image:caption': path.basename(imageUrl)}
-            ];
-            // Add the node to the url xml node
-            orig.url.push({
-                'image:image': imageEl
-            });
+            imageUrl = this.getUrlForImage(datum.cover);
+            imageUrl = imageUrl.substring(0, 2) === '//' ? 'http:' + imageUrl : imageUrl;
+            if (validator.isURL(imageUrl, {protocols: ['http', 'https'], require_protocol: true})) {
+                // Create the weird xml node syntax structure that is expected
+                imageEl = [
+                    {'image:loc': imageUrl},
+                    {'image:caption': path.basename(imageUrl)}
+                ];
+                // Add the node to the url xml node
+                orig.url.push({
+                    'image:image': imageEl
+                });
+            }
         }
 
         return orig;