MDL-50310 glossary: Fix restore of random glossary entry block

When restoring the random glossary entry block, we need to check that
the associated glossary has also been included in the backup and is
being restored. If not, we must invalidate the block configuration.

Before this patch, the block configuration was not invalidated.

Additionally, as a result of MDL-20131, the block configuration also
contains the course id of the associated glossary (which by the way does
not seem to be a wise choice, but I may be missing something). So we
need to remap this course id as well to avoid mismatch.

blocks/glossary_random/backup/moodle2/restore_glossary_random_block_task.class.php

@@ -62,9 +62,16 @@ public function after_restore() {
             if (!empty($config->glossary)) {
                 // Get glossary mapping and replace it in config
                 if ($glossarymap = restore_dbops::get_backup_ids_record($this->get_restoreid(), 'glossary', $config->glossary)) {
-                    $config->glossary = $glossarymap->newitemid;
+                    $mappedglossary = $DB->get_record('glossary', array('id' => $glossarymap->newitemid),
+                        'id,course,globalglossary', MUST_EXIST);
+                    $config->glossary = $mappedglossary->id;
+                    $config->courseid = $mappedglossary->course;
+                    $config->globalglossary = $mappedglossary->globalglossary;
                     $configdata = base64_encode(serialize($config));
                     $DB->set_field('block_instances', 'configdata', $configdata, array('id' => $blockid));
+                } else {
+                    // The block refers to a glossary not present in the backup file.
+                    $DB->set_field('block_instances', 'configdata', '', array('id' => $blockid));
                 }
             }
         }