Fix potentially uninitialized memory

[goncharov]

Summary

for https://github.com/llvm/llvm-project/commit/7d76d6095880f34914d85d876b260cc4a4ea640d

[goncharov]

updated patch prefix

[abrachet]

Thank you. Sorry about that!

[goncharov]

(landed as 4856bc16c651ec151b16e3d97704901ab6a1c383)

tools/driver/driver.cpp

   bool IsCrash = false;
   Driver::CommandStatus CommandStatus = Driver::CommandStatus::Ok;
   // Pretend the first command failed if ReproStatus is Always.
-  const Command *FailingCommand = &*C->getJobs().begin();
+  const Command *FailingCommand = nullptr;
+  if (!C->getJobs().empty())
+    FailingCommand = &*C->getJobs().begin();
+
   if (C && !C->containsError()) {
     SmallVector<std::pair<int, const Command *>, 4> FailingCommands;
     Res = TheDriver.ExecuteCompilation(*C, FailingCommands);

   // crash, but only if we're crashing due to FORCE_CLANG_DIAGNOSTICS_CRASH.
   if (::getenv("FORCE_CLANG_DIAGNOSTICS_CRASH"))
     llvm::dbgs() << llvm::getBugReportMsg();
-  if (TheDriver.maybeGenerateCompilationDiagnostics(CommandStatus, ReproLevel,
+   if (FailingCommand != nullptr &&
+      TheDriver.maybeGenerateCompilationDiagnostics(CommandStatus, ReproLevel,
                                                     *C, *FailingCommand))
     Res = 1;