event-editor: Fix widgets groups sensitivity sync
Brown paperbag fix. I hope sempai will forgive me
This is still compatible with !418 (merged) and !419, their code seems to work fine when combined with this locally.
A side-effect of changing the default "writable" state in commit 06b3c38d is that we must ensure that all the widget groups are synced with it.
Fixes #1178 (closed)