No error if cache path unaccessable

I migrated my firefox install from one computer to another a year or so back, changing usernames in the process. The cache folder for this addon was still set to /home/olduser/.mozilla/[etc], but instead of giving some kind of indication that it wasn't able to find/make the folder, it's just been failing silently all this time.

Perhaps it can be similar to the error that pops up when the editor binary/script can't be found.