Running an `user_defined_test` file errors due to missing `feedback_message`

[MrSerth]

In the current setup, running a user_defined_test (as test action) doesn't return any output. This is due to an implicit necessary feedback_message, which cannot and should not be configured for user_defined_test files.

An exception occurs in this line:

codeocean/app/models/submission.rb

Lines 329 to 335 in 445113e

	else
	# The render_markdown method from application_helper.rb is not available in model classes.
	ActionController::Base.helpers.sanitize(
	Kramdown::Document.new(file.feedback_message, smart_quotes: 'apos,apos,quot,quot').to_html,
	tags: %w[strong],
	attributes: []
	)

Most likely, Kramdown::Document.new doesn't accept file.feedback_message to be nil. A potential solution would be to switch the else to:

elsif output[:file_role] != 'user_defined_test'