[clang] Fix crash with -ast-dump=json (PR #137324)

[Aaron Ballman via cfe-commits]

================
@@ -211,6 +211,8 @@ Non-comprehensive list of changes in this release
 - Added `__builtin_elementwise_exp10`.
 - For AMDPGU targets, added `__builtin_v_cvt_off_f32_i4` that maps to the `v_cvt_off_f32_i4` instruction.
 - Added `__builtin_elementwise_minnum` and `__builtin_elementwise_maxnum`.
+- No longer crashing on invalid Objective-C extensions when dumping the AST as
----------------
AaronBallman wrote:

SGTM! I've updated

https://github.com/llvm/llvm-project/pull/137324