Adding new Coursework activity causes warning on 3.7 if "User to receive submission notification" box has no selection

[lexxkoto]

Hello,

Plugin works fine in Moodle 3.5, but in 3.7 it throws a warning when a new activity is created - but only if the 'User to receive submission notification' box doesn't have a selection.

This results in an empty array being passed through to add_moduleinfo() and is tripping up emulate_bound_params().

`

( ! ) Warning: mysqli::real_escape_string() expects parameter 1 to be string, array given in /var/www/moodle37/lib/dml/mysqli_native_moodle_database.php on line 1112

1 | 0.0000 | 383248 | {main}( ) | .../modedit.php:0
2 | 0.2373 | 9139248 | add_moduleinfo( ) | .../modedit.php:155
3 | 0.2393 | 9177640 | coursework_add_instance( ) | .../modlib.php:122
4 | 0.2395 | 9183272 | mariadb_native_moodle_database->insert_record( ) | .../lib.php:182
5 | 0.2399 | 9312392 | mariadb_native_moodle_database->insert_record_raw( ) | .../mysqli_native_moodle_database.php:1375
6 | 0.2400 | 9315104 | mariadb_native_moodle_database->emulate_bound_params( ) | .../mysqli_native_moodle_database.php:1324
7 | 0.2401 | 9317744 | real_escape_string ( ) | .../mysqli_native_moodle_database.php:1112

`