Fixed issue 'Expression has changed after it was checked' in viewer-app.component by manually triggering change detection

[vladimir-litvinchik]

Details about the error:

• https://blog.angular-university.io/angular-debugging/
• https://hackernoon.com/everything-you-need-to-know-about-the-expressionchangedafterithasbeencheckederror-error-e3fd9ce7dbb4
• https://stackoverflow.com/questions/34364880/expression-has-changed-after-it-was-checked

Solution - manually trigger change detection by calling this.cdr.detectChanges();