DocTab selection underline not updated when deleting an Item

[matwachich]

Checklist

• I have searched the issue tracker for open issues that relate to the same problem, before opening a new one.
• This issue only relates to a single bug. I will open new issues for any other problems.

Describe the bug

Deleting a tab item N, while N+1 is selected, will not update the selection underline bar.

How to reproduce

Run the code, add 3 tabs, select tab 2, close tab 1, see the selection bar is under tab 3 rather than 2

Screenshots

Example code

package main

import (
	"fmt"

	"fyne.io/fyne/v2/app"
	"fyne.io/fyne/v2/container"
	"fyne.io/fyne/v2/theme"
	"fyne.io/fyne/v2/widget"
)

func main() {
	a := app.New()
	w := a.NewWindow("Test")

	tab := container.NewDocTabs()

	count := 1
	btn := widget.NewButton("Add Tab", func() {
		tab.Append(container.NewTabItemWithIcon(
			fmt.Sprintf("Tab Item %d", count), theme.HomeIcon(), widget.NewLabel(fmt.Sprintf("Tab Content %d", count)),
		))
		tab.SelectIndex(len(tab.Items) - 1)
		count += 1
	})

	w.SetContent(container.NewBorder(btn, nil, nil, nil, tab))
	w.ShowAndRun()
}

Fyne version

develop v2.3.4-rc1.0.20230516195251-56dd0f3e0f32

Go compiler version

1.20

Operating system and version

Windows 10

Additional Information

No response

[matwachich]

Unfortunatly, this PR did not solve this bug report.

Try the code above :

• Add 3 tabs
• Select 2nd tab
• Close first tab

see selection bar not syncronized.

[andydotxyz]

Fixed on develop :)