Hopefully fix a mysterious MathJax bug

Summary:
I haven't investigated in a lot of detail but Sam reported that if you open a new-item page (with useKatex: false) and switch to expression entry then you get an exception from within .Text() because the script whose text it tries to set is missing.

Not sure why the queue was there, but I don't _think_ it's necessary. (I know that the outer one is.) Can't wait to get rid of MathJax.

Reviewers: emily

Reviewed By: emily

CC: sambirch

Differential Revision: http://phabricator.khanacademy.org/D3607