Thanks of created this addons, It saved my life a few time: Firefox closed while opening 2 windows, it can't use the built-in restore feature since it only able restore single window. I've sent 5 dollar to you just now :)

btw, Just now got indexedDB issue, I don't have to delete storage folder, I just have to goto about:profile, open the profile+cut that folder, then restart web browser and the error gone