Fix an error check re: sample variables

Bug: skia:
Change-Id: I89f2912ba18c27a3b2b99b99c13ec92a2cc3ebff
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/228572
Commit-Queue: Chris Dalton <csmartdalton@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed