Since the poll post handler runs very early in the post creation
process, it's possible to run the handler on an obiviously invalid post.
This change ensures the post's `raw` value is present before
proceeding.
This reduces chances of errors where consumers of strings mutate inputs
and reduces memory usage of the app.
Test suite passes now, but there may be some stuff left, so we will run
a few sites on a branch prior to merging
Selase Krakani
David Taylor
Loïc Guitaut
Phil Pirozhkov
Sam Saffron
Régis Hanol