closed tabs reappear when a virtual tab is realised

[the6p4c]

repro'd on both HEAD and the current web version:

• open two real tabs
• open a virtual tab (e.g. create a new document)
• close the two real tabs
• realise the virtual tab
• oops: the closed tabs reappear

[cpsdqs]

i suppose the whole document loading system is kinda jank and could do with a refactor… maybe this weekend i will do a little javascripts