Calendar: creating a course event fails with dmlreadexception

ERROR:  invalid input syntax for integer: "Array"

SELECT * FROM mdl_course WHERE id = $1

[array (

  0 => 

  array (

    0 => 2,

  ),

)]

Error code: dmlreadexception

* line 486 of /lib/dml/moodle_database.php: dml_read_exception thrown

* line 242 of /lib/dml/pgsql_native_moodle_database.php: call to moodle_database->query_end()

* line 778 of /lib/dml/pgsql_native_moodle_database.php: call to pgsql_native_moodle_database->query_end()

* line 1571 of /lib/dml/moodle_database.php: call to pgsql_native_moodle_database->get_records_sql()

* line 1543 of /lib/dml/moodle_database.php: call to moodle_database->get_record_sql()

* line 1522 of /lib/dml/moodle_database.php: call to moodle_database->get_record_select()

* line 131 of /calendar/classes/local/event/forms/create.php: call to moodle_database->get_record()

* line 590 of /lib/formslib.php: call to core_calendar\local\event\forms\create->validation()

* line 526 of /lib/formslib.php: call to moodleform->validate_defined_fields()

* line 3579 of /calendar/lib.php: call to moodleform->is_validated()

* line 7666 of /lib/moodlelib.php: call to calendar_output_fragment_event_form()

* line 415 of /lib/external/externallib.php: call to component_callback()

* line 228 of /lib/externallib.php: call to core_external::get_fragment()

* line 59 of /lib/ajax/service.php: call to external_api::call_external_function()