Closing last-positioned tab of a panel switches to next panel

[PWDSerialgamer07]

Steps to reproduce

• Open Firefox in a new profile
• Install Sidebery
• Set "Previous tab" behavior for "After closing tab", as well as "on" for "stay in panel to the last tab"
• Open multiple panels with tabs, all of them unloaded except for the first one
• Close the tab in the last position of the first panel

Actual behavior

Sidebery jumps to the tab in the first position of the next panel

Expected behavior

Sidebery goes to the tab before the one we jsut closed

System

Windows 11

Firefox version

Floorp Version 11.11.2

Sidebery version

5.2.0

Logs

No response

[nerradtreborsniktaw]

Same issue observed.

System

Windows 10

Firefox version

128.0

Sidebery version

5.2.0

[jpodolski]

Also affecting me.

Windows 10 (22H2) Firefox Developer Edition (129.0b9) Sidebery Ver. 5.2.0.8

Perhaps illuminating to note some details on reproducing:

1. Have a "Tab A" open and in use in "Panel A" (with some "Panel B" existing below, with open tabs)
2. Open a new tab ("Tab B") with Ctrl+T, or by double clicking the empty space in Panel A
3. In this "Tab B", navigate to some page that has links. Google search results work fine.
4. Open a link on "Tab B" such that it opens in a new child tab, "Tab B2". For example, with Ctrl+Click, or by clicking a link that spawns a new tab by default (e.g., Startpage search results).
5. Close this Tab B2, which will correctly focus Tab B.
6. Close Tab B. This will now incorrectly focus the first tab in Panel B, rather than Tab A in Panel A as expected

Importantly, Step 6 will only fail if Step 4 is executed (opening a child tab from Tab B). If you just close Tab B after step 3 (before creating a child tab), Sidebery will focus Tab A as expected. It seems that spawning a child tab has some effect on this bug.