From 0864c8a59dcad2c946eb3977cacae55f9ee14c99 Mon Sep 17 00:00:00 2001
From: Petr Skoda <commits@skodak.org>
Date: Sat, 20 Aug 2011 11:34:58 +0200
Subject: [PATCH] MDL-29022 do not require idnumber in ext courses - backport
 from MDL-29020

---
 enrol/database/lib.php | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/enrol/database/lib.php b/enrol/database/lib.php
index 987e0e73f96..bbe2e08b682 100644
--- a/enrol/database/lib.php
+++ b/enrol/database/lib.php
@@ -546,8 +546,8 @@ class enrol_database_plugin extends enrol_plugin {
                         // already exists
                         continue;
                     }
-                    if ($idnumber and $DB->record_exists('course', array('idnumber'=>$fields[$idnumber]))) {
-                        // idnumber duplicates are not allowed
+                    // allow empty idnumber but not duplicates
+                    if ($idnumber and $fields[$idnumber] !== '' and $fields[$idnumber] !== null and $DB->record_exists('course', array('idnumber'=>$fields[$idnumber]))) {
                         continue;
                     }
                     if ($category and !$DB->record_exists('course_categories', array('id'=>$fields[$category]))) {