fix(server): don't crash on setupExitSignals(undefined)

Not sure how it's possible as all callers pass an object, but observed in webpack#1479 (comment)

Author: cben

lib/utils/setupExitSignals.js

@@ -5,7 +5,7 @@ const signals = ['SIGINT', 'SIGTERM'];
 function setupExitSignals(serverData) {
  signals.forEach((signal) => {
  process.on(signal, () => {
- if (serverData.server) {
+ if (serverData && serverData.server) {
  serverData.server.close(() => {
  // eslint-disable-next-line no-process-exit
  process.exit();

test/server/utils/setupExitSignals.test.js

@@ -25,6 +25,16 @@ describe('setupExitSignals', () => {
  });
 
  signals.forEach((signal) => {
+ it(`should exit process (${signal}, serverData never defined`, (done) => {
+ // eslint-disable-next-line no-undefined
+ setupExitSignals(undefined);
+ process.emit(signal);
+ setTimeout(() => {
+ expect(exitSpy.mock.calls.length).toEqual(1);
+ done();
+ }, 1000);
+ });
+
  it(`should exit process (${signal}, server never defined)`, (done) => {
  setupExitSignals({
  server: null,