Fix warning when trying to render an empty feed

Change-Id: Iab7aac11915b19d0c3e306949513dfc90e6a82c6
Signed-off-by: Richard Mansfield <richard.mansfield@catalyst.net.nz>

htdocs/blocktype/externalfeed/lib.php

@@ -68,8 +68,10 @@ class PluginBlocktypeExternalfeed extends SystemBlocktype {
             $data->image   = unserialize($data->image);
 
             // only keep the number of entries the user asked for
+            if (count($data->content)) {
                 $chunks = array_chunk($data->content, isset($configdata['count']) ? $configdata['count'] : 10);
                 $data->content = $chunks[0];
+            }
 
             // Attempt to fix relative URLs in the feeds
             if (!empty($data->image['link'])) {