Pre build bug fix

src/app/ar-fan-cam/ar-fan-cam.page.ts

@@ -9,9 +9,9 @@ import { ModalController } from '@ionic/angular';
     styleUrls: ['./ar-fan-cam.page.scss'],
 })
 export class ArFanCamPage implements OnInit {
-    @ViewChild('videoElement', null) videoElement: ElementRef<HTMLVideoElement>;
-    @ViewChild('glassesElement', null) glassesElement: ElementRef<HTMLImageElement>;
-    @ViewChild('canvasElement', null) canvasElement: ElementRef<HTMLCanvasElement>;
+    @ViewChild('videoElement') videoElement: ElementRef<HTMLVideoElement>;
+    @ViewChild('glassesElement') glassesElement: ElementRef<HTMLImageElement>;
+    @ViewChild('canvasElement') canvasElement: ElementRef<HTMLCanvasElement>;
     
     mediaStream: MediaStream|null = null;
     capturedImageStrings: Array<string> = [];