[clang] [clang-format] Fix crash involving array designators (PR #77045)

[Owen Pan via cfe-commits]

owenca wrote:

> While I was trying to find a minimal reproducer to the bug, I accidentally found that this patch fix another crash, and doesn't fix the linked issue.

Can you open another pull request to [fix](https://github.com/llvm/llvm-project/pull/77045#discussion_r1442578220) the other crash?
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https://github.com/llvm/llvm-project/pull/77045