Fix fuzzer crash when casting between int and float.

The fix submitted at http://review.skia.org/335868 did not support
casts. The fuzzer discovered this shortcoming right away.

Change-Id: I2f5166528cee41367348564d4e664476fd5704ff
Bug: oss-fuzz:27650
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/336656
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
4 files changed