fix: pass unhandled error on to next express error handler

Commit 0ae6f54 introduced an error handling middleware.
However, it does not delegate to the next error handler if it cannot handle the error adequately.
This causes the request to hang until a timeout kills the connection.
By passing the error on to next, other error handlers (like the default error handler) handle it.

lib/loaders/express.loader.ts

@@ -83,6 +83,8 @@ export class ExpressLoader extends AbstractLoader {
           throw new NotFoundException(err.message);
         } else if (err?.code === 'ENOENT') {
           throw new NotFoundException(`ENOENT: ${err.message}`);
+        } else {
+          next(err);
         }
       });
     });

tests/e2e/express-adapter.e2e-spec.ts

@@ -9,6 +9,24 @@ describe('Express adapter', () => {
   let server: Server;
   let app: INestApplication;
 
+  describe('when middleware throws generic error', () => {
+    beforeAll(async () => {
+      app = await NestFactory.create(AppModule.withDefaults(), {
+        logger: new NoopLogger()
+      });
+      app.use((_req, _res, next) => next(new Error('Something went wrong')));
+
+      server = app.getHttpServer();
+      await app.init();
+    });
+
+    describe('GET /index.html', () => {
+      it('should return Iternal Server Error', async () => {
+        return request(server).get('/index.html').expect(500);
+      });
+    });
+  });
+
   describe('when "fallthrough" option is set to "true"', () => {
     beforeAll(async () => {
       app = await NestFactory.create(AppModule.withFallthrough(), {