Don't crash when a process' task port goes bad.
Don't crash when a process' task port goes bad.

<rdar://problem/26256049>

git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@269373 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 5b43fb0f8cecb0471dff2f6468c93dfc434b7c43)

apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb,apple/swift-lldb