From e35c7c2c50b836d9f03016aa61296c9a2d3ee685 Mon Sep 17 00:00:00 2001
From: Davo Smith <davo.smith@synergy-learning.com>
Date: Mon, 29 Oct 2018 09:26:58 +0000
Subject: [PATCH] MDL-63798 mod_assign: fix restore when group is missing

---
 mod/assign/backup/moodle2/restore_assign_stepslib.php | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/mod/assign/backup/moodle2/restore_assign_stepslib.php b/mod/assign/backup/moodle2/restore_assign_stepslib.php
index d4ba0a56a18..179f9ed4903 100644
--- a/mod/assign/backup/moodle2/restore_assign_stepslib.php
+++ b/mod/assign/backup/moodle2/restore_assign_stepslib.php
@@ -167,6 +167,11 @@ class restore_assign_activity_structure_step extends restore_activity_structure_
         }
         if (!empty($data->groupid)) {
             $data->groupid = $this->get_mappingid('group', $data->groupid);
+            if (!$data->groupid) {
+                // If the group does not exist, then the submission cannot be viewed and restoring can
+                // violate the unique index on the submission table.
+                return;
+            }
         } else {
             $data->groupid = 0;
         }