As noticed on the Learn Moodle site when some accounts were deleted by the privacy office - the following error message appeared:
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Exception occurred while calling core_blog\privacy\provider::delete_data_for_user.
This means that plugin core_blog did not complete the processing of data. The following exception information may be passed on to the plugin developer:

Coding error detected, it must be fixed by a programmer: moodle_database::get_in_or_equal() does not accept empty arrays

#0 /opt/app/blog/classes/privacy/provider.php(463): moodle_database->get_in_or_equal(Array, 1, 'param', true)
#1 /opt/app/lib/moodlelib.php(7880): core_blog\privacy\provider::delete_data_for_user(Object(core_privacy\local\request\approved_contextlist))
#2 /opt/app/privacy/classes/manager.php(578): component_class_callback('core_blog
priva...', 'delete_data_for...', Array)
#3 /opt/app/privacy/classes/manager.php(611): core_privacy\manager::component_class_callback('core_blog', 'core_privacy
lo...', 'delete_data_for...', Array)
#4 /opt/app/privacy/classes/manager.php(415): core_privacy\manager->handled_component_class_callback('core_blog', 'core_privacy
lo...', 'delete_data_for...', Array)
#5 /opt/app/admin/tool/dataprivacy/classes/task/process_data_request_task.php(134): core_privacy\manager->delete_data_for_user(Object(core_privacy\local\request\contextlist_collection))
#6 /opt/app/lib/cronlib.php(185): tool_dataprivacy\task\process_data_request_task->execute()
#7 /opt/app/lib/cronlib.php(74): cron_run_inner_adhoc_task(Object(tool_dataprivacy\task\process_data_request_task))
#8 /opt/app/admin/cli/cron.php(61): cron_run()
#9

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