message: fix(core): ViewContainerRef.indexOf doesn't throw error when empty
  PR Close
diff: @@ -186,7 +186,8 @@ export class ViewContainerRef_ implements ViewContainerRef {
  }
  indexOf(viewRef: ViewRef): number {
  - return this._element.nestedViews.indexOf((<ViewRef_<any>>viewRef).internalView);
  + return this.length ? this._element.nestedViews.indexOf((<ViewRef_<any>>viewRef).internalView) :
  + -1;
  }
  /** @internal */
  @@ -213,7 +214,7 @@ export class ViewContainerRef_ implements ViewContainerRef {
  return wtfLeave(s, view.ref);
  }
  - clear() {
  + clear(): void {
  for (let i = this.length - 1; i >= 0; i--) {
  this.remove(i);
  }
  