Fix assert

Change-Id: I23a88524d741cecefa16ae7e364d2294db1c6030
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/226508
Reviewed-by: Jim Van Verth <jvanverth@google.com>
Commit-Queue: Robert Phillips <robertphillips@google.com>
1 file changed