message: Don't ever try to pass "" as a starting directory, no way
  Fixes
diff: @@ -106,6 +106,8 @@ namespace winrt::Microsoft::Terminal::TerminalConnection::implementation
  siEx.StartupInfo.lpTitle = mutableTitle.data();
  }
  + const wchar_t* const startingDirectory = _startingDirectory.size() > 0 ? _startingDirectory.c_str() : nullptr;
  +
  RETURN_IF_WIN32_BOOL_FALSE(CreateProcessW(
  nullptr,
  cmdline.data(),
  @@ -114,7 +116,7 @@ namespace winrt::Microsoft::Terminal::TerminalConnection::implementation
  false, // bInheritHandles
  EXTENDED_STARTUPINFO_PRESENT | CREATE_UNICODE_ENVIRONMENT, // dwCreationFlags
  lpEnvironment, // lpEnvironment
  - _startingDirectory.c_str(),
  + startingDirectory,
  &siEx.StartupInfo, // lpStartupInfo
  &_piClient // lpProcessInformation
  ));
  