upgrade from 3.11.11+ to 4.1 shows several "Warning: Creating default object from empty value in /var/www/html/lib/db/upgrade.php on line 2336"

Environment setup Stand up an environment using MOODLE_311_STABLE Test scenario: 3.11 -> 4.0 Login to the site as an admin Create a new course Navigate to course options by clicking the settings cog Select questions Select import tab from the question bank Select Moodle XML format and choose the attached XML file Import the questions Navigate back to the course Create a new quiz Add some random questions to the quiz by selecting some random tags Go to your database console and run the following (This will create all sorts of invalid data in the quiz_slots_tags table): -- Correct tag, invalid slot id INSERT INTO mdl_quiz_slot_tags (slotid, tagid, tagname) VALUES (24, 3, 'tricky');   INSERT INTO mdl_quiz_slot_tags (slotid, tagid, tagname) VALUES (25, 3, 'tricky');   -- correct slot, invalid tag INSERT INTO mdl_quiz_slot_tags (slotid, tagid, tagname) VALUES (1, 57, 'invalidtag');   INSERT INTO mdl_quiz_slot_tags (slotid, tagid, tagname) VALUES (1, 58, 'anotherinvalidtag');   -- both slot and tag invalid INSERT INTO mdl_quiz_slot_tags (slotid, tagid, tagname) VALUES (11, 60, 'pureinvalidtag');   INSERT INTO mdl_quiz_slot_tags (slotid, tagid, tagname) VALUES (11, 61, 'anotherpureinvalidtag'); Check the quiz_slot_tags table and confirm the data added to the table. Now pull the 4.0 branch from this tracker: git fetch https: //git.in.moodle.com/moodle/integration.git MOODLE_400_STABLE && git checkout FETCH_HEAD Add the following to your config.php of your moodle instance to ensure any sorts of errors are visible in the console: @error_reporting(E_ALL | E_STRICT); $CFG->debug = (E_ALL | E_STRICT); Run the following command from the console to run the upgrade: php admin/cli/upgrade.php Confirm that there is no such error like the following: PHP Warning:  Creating default object from empty value in /var/www/moodle/mdl76509/moodle/lib/db/upgrade.php   Confirm that the upgrade finishes successfully.   Repeat the whole test with 4.1 and master branches.