Fill in missing Video keys for English videos from topic tree when generating dubbed video maps

Fix for #1524.

Summary of changes:
*Loop through missing videos and add their keys to English.

TODO: Use the API directly to sort this all out! (as per #1135).

LeBron asks, give:

![image](https://f.cloud.github.com/assets/1680573/2188976/d0ab2d16-980e-11e3-89e4-20c89e27909d.png)

@bcipolli This is the change you suggested, and it is tiny. Tested as per above.