Bug fixes:

1) Replaced isteacher call in fullname ($course undefined)
2) Initialised $options array

admin/roles/assign.php

@@ -64,7 +64,7 @@
     
     $participants = get_string("participants");
     $user = get_record('user', 'id', $userid);
-    $fullname = fullname($user, isteacher($course->id));
+    $fullname = fullname($user, has_capability('moodle/site:viewfullnames', $context));
 
     // we got a few tabs there
     if ($context->aggregatelevel == CONTEXT_USERID) {
@@ -161,6 +161,7 @@
         
     // this needs to check capability too
     $role = get_records('role');
+    $options = array();
     foreach ($role as $rolex) {
         if (user_can_assign($context, $rolex->id)) {
             $options[$rolex->id] = $rolex->name;