Blank screen after update to with beta 4


i updated an app to beta 4. I used a blank project added my code and did the steps from the post sticked on top of the forum.

My app works exactly one time after ionic run android on my phone. When i start it with the icon ont the phone or do a new ionic run android there is just a white screen.

With chrome inspect i can see an error:
TypeError: Cannot read property ‘next’ of undefined.

When i delete all my stuff, this error does not come, but the screen is still blank.

Any idea what i could have done wrong?