MDL-83353 output: fix icon output in classic activity navigation.

Prevent `$PAGE` debugging when loading navigation branches.

lib/ajax/getnavbranch.php

@@ -49,6 +49,7 @@ try {
     // This identifies the block instance requesting AJAX extension
     $instanceid = optional_param('instance', null, PARAM_INT);
 
+    $PAGE->set_url(new moodle_url('/lib/ajax/getnavbranch.php'));
     $PAGE->set_context(context_system::instance());
 
     // Create a global nav object

lib/navigationlib.php

@@ -2462,7 +2462,7 @@ class global_navigation extends navigation_node {
         $icon = new pix_icon(
             $activitydata->icon ?: 'monologo',
             get_string('modulename', $activitydata->modname),
-            $activitydata->modname
+            $activitydata->icon ? $activitydata->iconcomponent : $activitydata->modname,
         );
 
         // Prepare the default name and url for the node.