[PATCH] Fix unconditional dereference of a WeakVH in CGDebugInfo TypeCache

[David Blaikie]

  LGTM - though I wonder whether we should actually be using TrackingVH here (not sure when we're expecting to "lose" types like this).

  A specifically reproducible test case might be helpful to file as a "to investigate" sort of thing. (where we can replace the 'if' you're adding with an assert, then reduce the test case, etc and better understand what's going on here and why we end up in this situation)

http://llvm-reviews.chandlerc.com/D2944

BRANCH
  fix-weak-dbg-info

ARCANIST PROJECT
  clang