Ionic-app-scripts 0.0.43 build error

[11:08:20] ionic-app-scripts 0.0.43
[11:08:21] watch started …
[11:08:21] build dev started …
[11:08:21] clean started …
[11:08:21] clean finished in 5 ms
[11:08:21] copy started …
[11:08:21] transpile started …
[11:08:24] build dev failed: Cannot read property ‘length’ of undefined
[11:08:24] copy finished in 3.78 s
[11:08:25] watch ready in 3.84 s
[11:08:25] dev server running: http://localhost:8100/

after i update new debug mode,it say about problem with ‘length’ to make it build fail…i copy src to another ionic2(2.1.8) folder and it can run
i think maybe it problem work with gulp???

I am getting the same error. It works when I rollback to 0.0.39

how to rollback?
20 charcterts

To rollback, change the entry in package.json

@ionic/app-scripts”: “0.0.39”

Then update the package

npm update