Preview button on Upload Story Page is not Working when invalid Youtube link is entered

[Pamela Wang]

Description

The preview button is not working. After filling out all the fields in the upload story form, then pressing "Preview Story" I am getting a blank page. See below:

Steps to Reproduce

1. Upload A Story
2. Fill out all of the fields (including video link)
3. Click Preview Story

Result: Blank Screen
Expected Result: Preview Story Page

[Hanlin Cheng]

Closed in #353