[clang-tools-extra] [NFC] Fix uninitialized pointer field. (PR #117173)

[Aaron Ballman via cfe-commits]

================
@@ -23,7 +23,7 @@ AST_MATCHER(StringLiteral, isOrdinary) { return Node.isOrdinary(); }
 } // namespace
 
 UseStdPrintCheck::UseStdPrintCheck(StringRef Name, ClangTidyContext *Context)
-    : ClangTidyCheck(Name, Context),
+    : ClangTidyCheck(Name, Context), PP(PP),
----------------
AaronBallman wrote:

```suggestion
    : ClangTidyCheck(Name, Context), PP(nullptr),
```

https://github.com/llvm/llvm-project/pull/117173