Moving Toolbar Hides Other Toolbars

### Apache NetBeans version

Apache NetBeans 29

### What happened

All toolbars disappear when adjusting toolbar locations.

### Language / Project Type / NetBeans Component

_No response_

### How to reproduce

On a new installation of netbeans, create a project (should work with any project type). Turn on all the toolbars (View->Toolbars). Then drag the rightmost toolbar down slightly as though to create another row of toolbars. This causes the toolbars to all be hidden (I assume some kind of exception was generated).

This doesn't seem to work quite every time, but I've found it to be fairly repeatable. If it's not working, reset toolbars and start again.

https://github.com/user-attachments/assets/150735b6-95a6-43be-9595-d245934bd462

### Did this work correctly in an earlier version?

No / Don't know

### Operating System

Windows 11 Enterprise

### JDK

OpenJDK 22.0.1

### Apache NetBeans packaging

Apache NetBeans binary zip

### Anything else

I saw this in NB 20: https://github.com/apache/netbeans/issues/7017

It seemed to be resolved in NB 26, but since it's a bit intermittent I may have been wrong.

### Are you willing to submit a pull request?

No

Start by reproducing the toolbar sequence described on Windows 11 with Apache NetBeans 29: enable all toolbars, then drag the rightmost toolbar down slightly. Compare the behavior with issue 7017; done means adjusting toolbar locations no longer hides all toolbars.

Written by the indexing model from the issue text.