buffet: Don't deference privet if it's disabled

Refactoring in CL:285673 introduced crash on
nullptr if buffet started with --disable_privet

BUG=brillo:1242
TEST='FEATURES=test emerge-gizmo buffet'
     Run: buffet --disable_privet

Change-Id: I70bdc0118f69e6a64b6831bb3c2e713b8aebdd29
Reviewed-on: https://chromium-review.googlesource.com/286611
Trybot-Ready: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
1 file changed
tree: 9d8cf02b99fe966b4d9e9766162c5e0b5408d728
  1. buffet/