While testing MDLQA-7111,

1. I used test data set (Please contact me and I will see how I can share the dataset)
2. upgraded the site to 2.6 integration.
3. Upgraded to master integration and it failed at Upgrading quiz structure - 1018/6733 with

   Debug info: ERROR: invalid input syntax for integer: ""

   SELECT defaultmark FROM mdl_question WHERE id = $1

   [array (

   0 => '',

   )]

   Error code: dmlreadexception

   Stack trace:

   line 443 of /lib/dml/moodle_database.php: dml_read_exception thrown

   line 244 of /lib/dml/pgsql_native_moodle_database.php: call to moodle_database->query_end()

   line 764 of /lib/dml/pgsql_native_moodle_database.php: call to pgsql_native_moodle_database->query_end()

   line 1476 of /lib/dml/moodle_database.php: call to pgsql_native_moodle_database->get_records_sql()

   line 1549 of /lib/dml/moodle_database.php: call to moodle_database->get_record_sql()

   line 1530 of /lib/dml/moodle_database.php: call to moodle_database->get_field_sql()

   line 1509 of /lib/dml/moodle_database.php: call to moodle_database->get_field_select()

   line 613 of /mod/quiz/db/upgrade.php: call to moodle_database->get_field()

   line 697 of /lib/upgradelib.php: call to xmldb_quiz_upgrade()

   line 420 of /lib/upgradelib.php: call to upgrade_plugins_modules()

   line 1615 of /lib/upgradelib.php: call to upgrade_plugins()

   line 432 of /admin/index.php: call to upgrade_noncore()