Wrong tab selected after closing, intermittent

[personalmountains]

TST 4.0.18

This feels related to #3559 because I don't think it was happening before 4.0.18, but it's not caused by re-opening tabs. TST just seems to randomly select a different parent when closing a tab. Here's what I know:

• Closing a tab usually selects its parent correctly.
• Once in a while, a different tab is selected.
• It's usually the same wrong tab that's selected every time. I think it only selects a different bad tab when the other one is closed.
• The wrong tab seems to always be in a tree that's collapsed. This might be a coincidence, as most of my tabs are collapsed.

I can't reproduce it consistently, but it happens regularly, maybe after every 20-30 tabs I close. It happens really often.

I caught it once with TST's debug mode enabled. I'm attaching the logs from when I closed the tab, as well as my settings. In the logs:

• I closed tab #4360.
• It should have selected tab #16.
• It selected tab #3392 instead. This tab is always getting selected right now when TST selects the wrong one.
• I see two Tabs.onActivating, the first one is for #16, followed by #3392.

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