[clang-format][NFC] Skip ObjCHeaderStyleGuesser for empty code (#82957)

Author: owenca

clang/lib/Format/Format.cpp

@@ -3923,7 +3923,7 @@ FormatStyle::LanguageKind guessLanguage(StringRef FileName, StringRef Code) {
     auto Extension = llvm::sys::path::extension(FileName);
     // If there's no file extension (or it's .h), we need to check the contents
     // of the code to see if it contains Objective-C.
-    if (Extension.empty() || Extension == ".h") {
+    if (!Code.empty() && (Extension.empty() || Extension == ".h")) {
       auto NonEmptyFileName = FileName.empty() ? "guess.h" : FileName;
       Environment Env(Code, NonEmptyFileName, /*Ranges=*/{});
       ObjCHeaderStyleGuesser Guesser(Env, getLLVMStyle());