When I tried to "Download all submissions" for the assignment which has "Online text" submission type, the downloaded zip has broken and couldn't be opened.

It's happening in ver 3.11 or 4.0. not before 3.10.

Step to reproduce the issue:

1. Create a course.
2. Create an assignment activity with "Online text" Submission types.
3. Submit an assignment with "Online text".
4. Go to activity view page and choose "Download all submissions" from cog menu on the right side.

I can see the error below in vanilla moodle:

Exception - Argument 2 passed to core_files\local\archive_writer\zip_writer::add_file_from_stored_file() must be an instance of stored_file, array given, called in [dirroot]/mod/assign/locallib.php on line 3658

More information about this error

×Debug info:
Error code: generalexceptionmessage
×Stack trace:
line 112 of /files/classes/local/archive_writer/zip_writer.php: TypeError thrown
line 3658 of /mod/assign/locallib.php: call to core_files\local\archive_writer\zip_writer->add_file_from_stored_file()
line 652 of /mod/assign/locallib.php: call to assign->download_submissions()
line 55 of /mod/assign/view.php: call to assign->view() 

It looks the issue is from regression of MDL-68533