fix up preferences script
fix up preferences script

- tweak the null check
- reword the email association email
This fixes #47 and also addresses #40

Humbedooh/ponymail,quenda/ponymail,Humbedooh/ponymail,quenda/ponymail,jimjag/ponymail,quenda/ponymail,jimjag/ponymail,Humbedooh/ponymail,jimjag/ponymail,jimjag/ponymail