fix skslc crash when ternary parameter types don't match

BUG=skia:5968

Change-Id: I541c7925ac83e830bd53015961312810042046c5
Reviewed-on: https://skia-review.googlesource.com/6545
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
2 files changed