I running a redmine 5.0.5.stable in docker based on the docker official image. After installed redminex-ck-editor I found pictures over 110k can't be uploaded.
Error Message:
Completed 500 Internal Server Error in 29ms (ActiveRecord: 20.2ms)
TypeError (no implicit conversion of nil into String):
lib/redmine/sudo_mode.rb:61:in `sudo_mode'
Is there any place where this limit can be set? or something need to be set in order to upload images using ckeditor

This fix work for me
Regards