Fix JDWP crash when reporting exception

The exception's throw location may be null so we need to handle that
case. Also fixes a memset issue.

Bug: 17571297
(cherry picked from commit bbb63897d7f2d99219cb50721fe530521e08ddff)

Change-Id: Iedebb58f9460c5f04913c269200e51161bda1ba9
2 files changed