message: fix(core): workaround on angular issue with isProdMode
  fixes
diff: import { isDevMode } from '@angular/core';
  -
  const _messagesHash: { [key: string]: boolean } = {};
  -const _hideMsg = !isDevMode() || typeof console === 'undefined' || !console.warn;
  +const _hideMsg = typeof console === 'undefined' || !console.warn;
  export function warnOnce(msg: string): void {
  - if (_hideMsg || msg in _messagesHash) {
  + if (!isDevMode() || _hideMsg || msg in _messagesHash) {
  return;
  }
  