[clang] [NFC] Avoid potential null dereference. (PR #126872)

[Björn Schäpers via cfe-commits]

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@@ -1596,7 +1596,7 @@ static auto computeNewlines(const AnnotatedLine &Line,
     if (Line.startsWith(TT_NamespaceRBrace)) {
       if (Style.WrapNamespaceBodyWithEmptyLines == FormatStyle::WNBWELS_Never)
         Newlines = 1;
-      else if (!PreviousLine->startsWith(TT_NamespaceRBrace))
+      else if (PreviousLine && !PreviousLine->startsWith(TT_NamespaceRBrace))
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HazardyKnusperkeks wrote:

As owen said, we need a test case.

If `Line` starts with a closing namespace, I don't see how there could not be a `PreviousLine`.

https://github.com/llvm/llvm-project/pull/126872