[clang-tidy][NFC] Fix uninitialized pointer field. (#117173)

Non-static class member `PP` is not initialized in this constructor nor
in any functions that it calls.

Author: zahiraam

clang-tools-extra/clang-tidy/modernize/UseStdPrintCheck.cpp

@@ -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(nullptr),
       StrictMode(Options.getLocalOrGlobal("StrictMode", false)),
       PrintfLikeFunctions(utils::options::parseStringList(
           Options.get("PrintfLikeFunctions", ""))),
@@ -131,6 +131,7 @@ void UseStdPrintCheck::check(const MatchFinder::MatchResult &Result) {
   utils::FormatStringConverter::Configuration ConverterConfig;
   ConverterConfig.StrictMode = StrictMode;
   ConverterConfig.AllowTrailingNewlineRemoval = true;
+  assert(PP && "Preprocessor should be set by registerPPCallbacks");
   utils::FormatStringConverter Converter(
       Result.Context, Printf, FormatArgOffset, ConverterConfig, getLangOpts(),
       *Result.SourceManager, *PP);