There's nothing in the log because the fonts are changed outside of the lua context, so it can't really throw a stack trace into the log, but there's probably a way to add something into the log regardless. The addon tells the plugin to load a font with some settings, the plugin does it between the next frames for the addons.
There definitely are some cases to fix in the error handling and I'll try to fix that this week, as well as add something to tell you that it failed to load a font and at least an error code. With those fixes, at least it'll revert to the old default bitmap font that's embedded in the plugin. I'll probably also add a way to disable the settings editor from the configuration menu as well.