message: Fix null pointer dereference of param.primary_file
diff: @@ -1932,6 +1932,8 @@ std::vector<std::unique_ptr<IndexFile>> ParseWithTu(
  perf->index_build = timer.ElapsedMicrosecondsAndReset();
  std::unordered_map<std::string, int> inc_to_line;
  + // TODO
  + if (param.primary_file)
  for (auto &inc : param.primary_file->includes)
  inc_to_line[inc.resolved_path] = inc.line;
  @@ -1940,6 +1942,7 @@ std::vector<std::unique_ptr<IndexFile>> ParseWithTu(
  entry->import_file = file;
  entry->args = args;
  + if (param.primary_file) {
  // If there are errors, show at least one at the include position.
  auto it = inc_to_line.find(entry->path);
  if (it != inc_to_line.end()) {
  @@ -1953,6 +1956,7 @@ std::vector<std::unique_ptr<IndexFile>> ParseWithTu(
  break;
  }
  }
  + }
  // Update file contents and modification time.
  entry->file_contents_ = param.file_contents[entry->path].contents;
  