Does anyone know what this error indicates? When I get to the stage of previewing uploads on GWT, I get a page with just this: Exception encountered, of type "Wikimedia\Assert\ParameterAssertionException"
I've tried swapping around parameters and I'm using the most basic information template, which takes very few parameters anyway. The upload is explained at https://commons.wikimedia.org/wiki/Commons:Batch_uploading/Codex_Aureus
Thanks, Fae