Packaging an environment fails if package meta data does not include channels information

[AnastasiaSliusar]

At the moment, we do not have any default value, if a channel is not found for a package.

[martinRenou]

How do you reproduce this exactly?

I had this for pip packages and fixed it in #122. I'm wondering if you're simply not running latest empack?

[martinRenou]

I'm a bit worried about using "default" in the suggested change. So I'd prefer us to be extra careful and fix the actual issue if there is one still, instead of fixing the symptom only.