There is an issue with timeouts when uploading images. We haven't been able to get to the bottom of it, and our hope is that it will resolve when we upgrade. The good news is that the issue is intermittent. If you reload and try again at a different time, you may have more luck. Or if you've got another mod on the community, try and get them to upload it
Sounds like you are trying to parse the server response as a JSON object and that response doesn't actually contain such object. Someone may need to replicate the issue and see what is actually being returned from the server instead of the expected object.
Not a terribly helpful response I know.