swift234

Runtime: Fix memory safety violation in getEnumMirrorInfo()

This got flagged by the ASan bot once "Enable reflection for multi-payload
enums with non-trivial layout" went in, but the problem existed all along.

The field types array is only as large as the number of payload cases, but
we were loading from it unconditionally. We would set payloadType to nullptr
afterwards anyway in this case, but indirect was potentially wrong.

Swift SVN r30533