--theme option does not work

```shell
[sam@thinkpad-pro ~]$ wpg --theme base16-dracula
[i] theme         Set theme to base16-dracula.json.
[i] export        Exported json.
[e] image         No valid image file found.
```
good evening. This command seems to have a mind of it's own when running. Sometimes it works, sometimes I get this output. I cannot seem to narrow down what the cause it for this.