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

[Owen Pan via cfe-commits]

================
@@ -1444,7 +1444,8 @@ WhitespaceManager::CellDescriptions WhitespaceManager::getCells(unsigned Start,
       } else if (C.Tok->is(tok::comma)) {
         if (!Cells.empty())
           Cells.back().EndIndex = i;
-        if (C.Tok->getNextNonComment()->isNot(tok::r_brace)) // dangling comma
+        const FormatToken *Next = C.Tok->getNextNonComment();
+        if (Next && Next->isNot(tok::r_brace)) // dangling comma
           ++Cell;
----------------
owenca wrote:

```suggestion
        if (const auto *Next = C.Tok->getNextNonComment();
            Next && Next->isNot(tok::r_brace)) { // dangling comma
          ++Cell;
        }
```

https://github.com/llvm/llvm-project/pull/77045