HDR Gradient Editor window Color Picker closes when undoing color selection

Steps to reproduce:

1. Create a new URP project
2. Create a new Lit Shader Graph (Assets > Create > Shader Graph > URP > Lit Shader Graph)
3. Right-click and add Sample Gradient node
4. Click on the Color Picker property next to Gradient (G)
5. Observe the HDR Gradient Editor window opens
6. Click on the Color property to open Color Picker
7. Make any change
8. Click Undo/Ctrl+Z
9. Observe the Color Picker window

Actual results: The Color Picker window closes 

Expected results: The Color Picker window remains open

Reproducible with versions: 6000.0.78f1, 6000.5.1f1

Can’t test with versions: 6000.3.18f1, 6000.4.12f1, 6000.5.0f1, 6000.6.0a7 (this issue can only be observed after [Internal link] fix, because before the fix, the whole window would close)

Tested on (OS): Ubuntu 24.04, macOS 26.5