Fix clang-format segfault.

When annotating "lines" starting with ":", clang-format would segfault.
This could actually happen in valid code, e.g.
  #define A :

llvm-svn: 177283

1 files changed, 2 insertions, 0 deletions

diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
index 8267a25d031..4ac4c9b1b85 100644
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -319,6 +319,8 @@ private:
         Tok->Type = TT_ObjCMethodSpecifier;
       break;
     case tok::colon:
+      if (Tok->Parent == NULL)
+        return false;
       // Colons from ?: are handled in parseConditional().
       if (Tok->Parent->is(tok::r_paren) && Contexts.size() == 1) {
         Tok->Type = TT_CtorInitializerColon;