Repo tab order is not preserved after closing and reopening

Easiest way to replicate this is:

• have two repositories in the viewer on the left
• double click each of them to open them
• drag the second (right) tab to the left so that it becomes the first (left) tab
• close source tree
• reopen and the positions are now reversed again to the order they were initially opened

It should remember where it was when it was closed.