message: Make the tail-call handling code more resilient to weird debug info.
  rdar://problem/46494956
diff: @@ -147,6 +147,8 @@ void CallEdge::ParseSymbolFileAndResolve(ModuleList &images) {
  lazy_callee.symbol_name);
  auto resolve_lazy_callee = [&]() -> Function * {
  + if (!lazy_callee.symbol_name)
  + return nullptr;
  ConstString callee_name{lazy_callee.symbol_name};
  SymbolContextList sc_list;
  size_t num_matches =
  