Reject illegal file attributes in remote evaluation

Remove ! from reject illegal file parameters

app/controllers/concerns/file_parameters.rb

@@ -1,6 +1,20 @@
+# frozen_string_literal: true
+
 module FileParameters
+  def reject_illegal_file_attributes(exercise_id, params)
+    if Exercise.exists?(id: exercise_id) && params
+      params.reject do |_, file_attributes|
+        file = CodeOcean::File.find_by(id: file_attributes[:file_id])
+        file.nil? || file.hidden || file.read_only
+      end
+    else
+      []
+    end
+  end
+  private :reject_illegal_file_attributes
+
   def file_attributes
-    %w(content context_id feedback_message file_id file_type_id hidden id name native_file path read_only role weight file_template_id)
+    %w[content context_id feedback_message file_id file_type_id hidden id name native_file path read_only role weight file_template_id]
   end
   private :file_attributes
 end