Varset: Editing values in property pane, ESC confirms value entered, it should reset it to its previous value

### Problem description

As per the title.
Tested in V1.1.1 and the below mentioned dev version.
Safemode has no effect on this problem.

Assume the property has the value zero. Type some other non zero value and press escape.
Your property now has that non zero value that you intended to cancel.

You can UNDO this action with the expected return to your previous value.

### Workbench affected?

None

### Steps to reproduce

see description

### Expected behavior

see description

### Actual behavior

see description

### Development version About Info (in Safe Mode)

```shell
OS: Linux Mint 22.3 (X-Cinnamon/cinnamon/xcb)
Architecture: x86_64
Version: 26.3.0dev.20260623 (Git shallow) AppImage
Build date: 2026/06/23 18:37:30
Build type: Release
Branch: (HEAD detached at 0d88b4ad4)
Hash: 0d88b4ad4e221f05028ac623d15f49f2f2daf626
Python 3.11.14, Qt 6.8.3, Coin 4.0.3, Vtk 9.3.1, boost 1_86, Eigen3 3.4.0, PySide 6.8.3
shiboken 6.8.3, xerces-c 3.3.0, Clipper2 , IfcOpenShell 0.8.0, OCC 7.8.1
Locale: English/United Kingdom (en_GB)
Stylesheet/Theme/QtStyle: FreeCAD.qss/FreeCAD Dark/
Navigation Style/Orbit Style/Rotation Mode: Blender/Free Turntable/Window center
Logical DPI/Physical DPI/Pixel Ratio: 96/91.7938/1
Installed mods:
* StartUps
```

### Last known good version (optional)

```shell

```

Reproduce the issue in FreeCAD's Varset property pane by editing a zero value and pressing Escape. No source file or test is named; trace the property editor's Escape handling and verify that cancellation restores the previous value while the existing undo behavior remains intact.

Written by the indexing model from the issue text.