Merged from MOODLE_14_STABLE: Fixes in datalib and backuplib for postgres invalid sql

backup/backuplib.php

@@ -9,7 +9,7 @@
         $status = true;
         $status = execute_sql("INSERT INTO {$CFG->prefix}backup_ids
                                    (backup_code, table_name, old_id)
-                               SELECT DISTINCT '$backup_unique_code','quiz_categories',t.category
+                               SELECT DISTINCT $backup_unique_code,'quiz_categories',t.category
                                FROM {$CFG->prefix}quiz_questions t,
                                     {$CFG->prefix}quiz_question_grades g,
                                     {$CFG->prefix}quiz q

lib/datalib.php

@@ -2029,7 +2029,7 @@ function get_courses_page($categoryid="all", $sort="c.sortorder ASC", $fields="c
     global $USER, $CFG;
 
     $categoryselect = "";
-    if ($categoryid != "all") {
+    if ($categoryid != "all" && is_numeric($categoryid)) {
         $categoryselect = "c.category = '$categoryid'";
     }