Inspector: Multiple nodes selection breaks @export_group reset (properties shown in wrong group)

### Tested versions

Godot v4.6-rc2

### System information

Godot v4.6.rc2 - Windows 11 (build 26100) - Multi-window, 1 monitor - OpenGL 3 (Compatibility) - NVIDIA GeForce RTX 3050 Laptop GPU (NVIDIA; 32.0.15.9174) - 12th Gen Intel(R) Core(TM) i5-12500H (16 threads) - 31.71 ГиБ memory

### Issue description

When selecting multiple nodes of the same type, resetting the group via @export_group(“”, “”) is ignored, and subsequent properties are incorrectly attributed to the previous group

### Steps to reproduce

single choice

multiple choice

```
extends Node
class_name TestGroup

@export_group("group")
@export var in_group: bool

@export_group("", "")
@export var not_in_group: bool

@export_group("new_group")
@export var in_new_group: bool

@export_group("", "")

```

### Minimal reproduction project (MRP)

N/A

Reproduce the issue in the Godot Inspector with the provided TestGroup script, first comparing single-node and multiple-node selection. Verify the export groups shown for in_group, not_in_group, and in_new_group; done when resetting with @export_group("", "") keeps subsequent properties out of the previous group in both cases.

Written by the indexing model from the issue text.