Output only black image? #76

Describe the bug
I installed sdkit and downloaded a model (512-base-ema.ckpt). Now, I run the example script shown under "Local model" on the GitHub start page. The script runs with a lot of output, but there is no error. The result is just a black image with no content at all.

To Reproduce
Follow the installation instructions (Python 3.8) and execute the example script, using the 512-base-ema.ckpt model.

Expected behavior
An image with an astronaut :-)

Screenshots
Just black image

Environment (please complete the following information):

• OS (with OS version): Win 11
• Python version: 3.8 with miniforge / mamba environment

Additional context
Add any other context about the problem here.