fix running poutine without a config file

[becojo]

In this repo if you delete the file .poutine.yml and run poutine you get the following error:

$ go run . analyze_local .
{"level":"error","error":"open .poutine.yml: no such file or directory","time":"2024-05-09T11:44:21-04:00","message":"Can't read config"}

Viper does not return a viper.ConfigFileNotFoundError if viper.SetConfigFile is used.