Include shuffle within transcript when empty prior to a new major version release

[CPerezz]

Just realized the change might lead to different transcript_repr even the circuit doesn't use shuffle, so I think to keep backward compatability we need to skip the shuffle field when it's empty.

Originally posted by @han0110 in #195 (comment)

[davidnevadoc]

Doesn't the comment say the opposite? @CPerezz

[CPerezz]

Doesn't the comment say the opposite? @CPerezz

That's why I say "prior to a new major release". By that I mean that we can just assume we break backwards compatibility with a new major version release.
Hence we don't care more about this.