Bugfix: Export pac from a FixedProfile without bypass list do not work.

If a fixedProfle without any bypass list, pac generation will fail. This cause
export pac failure, and switch profile which refer to this fixedprofile also not
work properly.
Merge pull request #101 from LeeXiaolan/empty-bypass-list-bug

Bugfix: Export pac from a FixedProfile without bypass list do not work.