Add: 204-Error to permanentErrors-Array

When uploading there is a HTTP-404 logged to the console every checked chunk, so there is so much logging taking place it is hard to see real errors on the console.
Adding a HTTP-204 would give server-implementations a chance to return this statuscode for signaling the chunk is not available yet (204 - no content). The benefit would be you can find real errors on the console again.