message: fuzz: fix use of literal in default initialization.
  We hit
  on Google import.
diff: @@ -11,9 +11,9 @@ namespace Envoy {
  namespace Fuzz {
  // Convert from test proto Headers to TestHeaderMapImpl.
  -inline Http::TestHeaderMapImpl
  -fromHeaders(const test::fuzz::Headers& headers,
  - const std::unordered_set<std::string>& ignore_headers = {}) {
  +inline Http::TestHeaderMapImpl fromHeaders(
  + const test::fuzz::Headers& headers,
  + const std::unordered_set<std::string>& ignore_headers = std::unordered_set<std::string>()) {
  Http::TestHeaderMapImpl header_map;
  for (const auto& header : headers.headers()) {
  // HeaderMapImpl and places such as the route lookup should never see strings with embedded NULL
  