Open new private tab from "TabClose" event handler, if someone cancels "last-pb-context-exiting"
(workaround for #53, part 1)
Do nothing in toggleTabPrivate(), if someone cancels "last-pb-context-exiting"
(workaround for #53, part 2)
Forbid closing window with private tabs, if someone cancels "last-pb-context-exiting"
(workaround for #53, part 3)
Do nothing, if someone already prevent window closing
(workaround for #53, part 4; also related to #36 in SeaMonkey)
Don't check for last private tab closing, if user allow close entire window
(workaround for #53, part 5)