Fix handling of SkSL nullable FPs

Bug: skia:8798
Change-Id: Iec311c9d834a6f35b0a4481dbd748532107cd4b1
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/197108
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: Florin Malita <fmalita@chromium.org>
2 files changed