fix: add null check for connection.headers

lib/servers/SockJSServer.js

@@ -64,7 +64,7 @@ module.exports = class SockJSServer extends BaseServer {
   // f should be passed the resulting connection and the connection headers
   onConnection(f) {
     this.socket.on('connection', (connection) => {
-      f(connection, connection.headers);
+      f(connection, connection ? connection.headers : null);
     });
   }
 

test/server/servers/SockJSServer.test.js

@@ -10,7 +10,7 @@ describe('SockJSServer', () => {
   let socketServer;
   let listeningApp;
 
-  beforeAll((done) => {
+  beforeEach((done) => {
     // eslint-disable-next-line new-cap
     const app = new express();
 
@@ -84,9 +84,20 @@ describe('SockJSServer', () => {
         done();
       }, 3000);
     });
+
+    it('should not throw an exception when connection is null', () => {
+      const cb = jest.fn();
+
+      socketServer.onConnection(cb);
+
+      expect(() => {
+        socketServer.socket.emit('connection', null);
+      }).not.toThrow();
+      expect(cb.mock.calls[0]).toEqual([null, null]);
+    });
   });
 
-  afterAll((done) => {
+  afterEach((done) => {
     listeningApp.close(done);
   });
 });