refactor: forgotten input with strict typings

Author: maxime1992

src/app/child/child.component.ts

@@ -1,13 +1,14 @@
 import { ChangeDetectionStrategy, Component, Input } from '@angular/core';
 import { getObservableLifecycle } from 'ngx-observable-lifecycle';
+import { Nilable } from 'tsdef';
 
 @Component({
   selector: 'app-child',
   templateUrl: './child.component.html',
   changeDetection: ChangeDetectionStrategy.OnPush,
 })
 export class ChildComponent {
-  @Input() input: number;
+  @Input() input: Nilable<number>;
 
   constructor() {
     const {