glandium/about-startup — comment on commit 1cc359f9dca717812ec9d2f981b80820a960a168
File: bootstrap.js line 65
By xabolcs:

You cleaned up too much in this call.
If a user disables the addon then `aReason != APP_SHUTDOWN`
and the patchTBWindow should remove the menuitem (instead leaving it to window destroy)!

(Same issue at L62 - `StartupData.save()` - dataloss (not really, but negative values) could occured at addon shutdown too, not just when crashing.)