guard against deserializing bad values for VertexFiller
guard against deserializing bad values for VertexFiller

Bug: oss-fuzz:46251

Change-Id: I4bed79ab085860030732d29eaa674b59ea3d2808
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/526521
Reviewed-by: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>
Commit-Queue: Herb Derby <9e12a3d2bbf73546e47cc9958f6ba8f3215b7eaf@google.com>

google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia