validation: update api to yield a better error

validation/src/upload_submission.rs

@@ -4,6 +4,7 @@ use crate::nats_types::UploadSubmissionRequest;
 #[derive(Debug)]
 pub enum Error{
 	GetLocation(rbx_asset::cloud::GetError),
+	NonFreeModel,
 	Get(rbx_asset::cloud::GetError),
 	Json(serde_json::Error),
 	Create(rbx_asset::cookie::CreateError),
@@ -25,6 +26,11 @@ impl crate::message_handler::MessageHandler{
 			version:upload_info.ModelVersion,
 		}).await.map_err(Error::GetLocation)?;
 
+		// if the location does not exist, you are not allowed to donwload it
+		let Some(location)=location.location else{
+			return Err(Error::NonFreeModel);
+		};
+
 		// download the map model
 		let model_data=self.cloud_context.get_asset(&location).await.map_err(Error::Get)?;