MDL-31314 gradebook restore: fix category.depth on restore.

Without this, restoring backups made with the OU's custom 'restore from
1.9' feature, and possibly other people's custom converstion code, does
not work properly.

Also, fix poor recordset code.

backup/moodle2/restore_stepslib.php

@@ -371,40 +371,35 @@ protected function after_execute() {
         }
         $rs->close();
 
-        //need to correct the grade category path and parent
+        // Need to correct the grade category path and parent
         $conditions = array(
             'courseid' => $this->get_courseid()
         );
-        $grade_category = new stdclass();
 
         $rs = $DB->get_recordset('grade_categories', $conditions);
-        if (!empty($rs)) {
-            //get all the parents correct first as grade_category::build_path() loads category parents from the DB
-            foreach($rs as $gc) {
-                if (!empty($gc->parent)) {
-                    $grade_category->id = $gc->id;
-                    $grade_category->parent = $this->get_mappingid('grade_category', $gc->parent);
-                    $DB->update_record('grade_categories', $grade_category);
-                }
+        // Get all the parents correct first as grade_category::build_path() loads category parents from the DB
+        foreach ($rs as $gc) {
+            if (!empty($gc->parent)) {
+                $grade_category = new stdClass();
+                $grade_category->id = $gc->id;
+                $grade_category->parent = $this->get_mappingid('grade_category', $gc->parent);
+                $DB->update_record('grade_categories', $grade_category);
             }
         }
-        if (isset($grade_category->parent)) {
-            unset($grade_category->parent);
-        }
         $rs->close();
 
+        // Now we can rebuild all the paths
         $rs = $DB->get_recordset('grade_categories', $conditions);
-        if (!empty($rs)) {
-            //now we can rebuild all the paths
-            foreach($rs as $gc) {
-                $grade_category->id = $gc->id;
-                $grade_category->path = grade_category::build_path($gc);
-                $DB->update_record('grade_categories', $grade_category);
-            }
+        foreach ($rs as $gc) {
+            $grade_category = new stdClass();
+            $grade_category->id = $gc->id;
+            $grade_category->path = grade_category::build_path($gc);
+            $grade_category->depth = substr_count($grade_category->path, '/') - 1;
+            $DB->update_record('grade_categories', $grade_category);
         }
         $rs->close();
 
-        //Restore marks items as needing update. Update everything now.
+        // Restore marks items as needing update. Update everything now.
         grade_regrade_final_grades($this->get_courseid());
     }
 }