From 9b38aca0ce3ddad5ac51c480ded689a07cbf92c0 Mon Sep 17 00:00:00 2001
From: Tim Hunt <T.J.Hunt@open.ac.uk>
Date: Tue, 29 Apr 2014 11:41:16 +0100
Subject: [PATCH] MDL-45321 quiz upgrade: make it more tolerant to old bad
 data.

---
 mod/quiz/db/upgrade.php | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mod/quiz/db/upgrade.php b/mod/quiz/db/upgrade.php
index 7cfab3b78b3..21f4508f9da 100644
--- a/mod/quiz/db/upgrade.php
+++ b/mod/quiz/db/upgrade.php
@@ -588,6 +588,14 @@ function xmldb_quiz_upgrade($oldversion) {
                         continue;
                     }
 
+                    if ($questionid === '') {
+                        // This can happen as the result of old restore bugs.
+                        // There can be a missing number in the list of ids.
+                        // All we can do about this is ignore it, which is what
+                        // the quiz system used to do. See MDL-45321.
+                        continue;
+                    }
+
                     if (array_key_exists($questionid, $questionidtoslotrowid)) {
                         // Normal case. quiz_slots entry is present.
                         // Just need to add slot and page.