Looks like the config file for supplementaries is broken, you could try deleting it.
If it errors out again, scan through the log for similar errors to this, I've seen cases where the whole config folder needed to be nuked because they were all broken before the pack would load.
There is not enough information here to go on.
The best thing would be a link to a github repo with the project, then anyone that may be able to help can see the code/files/structure and possibly see where you are going wrong.