Drop line not rendered after auto-expansion

### Apache NetBeans version

Apache NetBeans 22

### What happened

Drop line is not rendered after auto-expansion, but it should

https://github.com/user-attachments/assets/d2aa1737-91e7-4f8e-b779-7289e63fc9a7

### Language / Project Type / NetBeans Component

_No response_

### How to reproduce

1. Drag an object a tree view (e.g. the Projects explorer) it; you’ll see a horizontal line when hovering between two objects to indicate the target position
2. Keep dragging and hover over an expandable object (e.g. a folder) which will then auto-expand

After the auto-expansion, hovering between objects no longer renders the horizontal line. I would expect the drop line to continue to be rendered even after the auto-expansion.

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

No / Don't know

### Operating System

Windows, Mac, Linux

### JDK

21.0.3 (and others)

### Apache NetBeans packaging

Apache NetBeans provided installer

### Anything else

_No response_

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

No

Reproduce the issue by dragging an item in the Projects explorer, hovering over an expandable object, and then checking the position between child objects after auto-expansion. Trace the Projects explorer tree drag-and-drop entry point and compare rendering before and after expansion. Done means the horizontal drop line remains visible after auto-expansion on the supported operating systems.

Written by the indexing model from the issue text.