Ionic builder app error help please

(node:3688) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch().

screenshot: https://i.stack.imgur.com/N4w81.jpg

Hi, I am monitoring your ionic 3 training that you have prepared, but I am constantly getting a compilation error and would like your help.