Unable to cancel Layout change when a dirty Timeline window is open

Steps to reproduce:

1. Create and open a new project
2. Open 'Window -> Sequencing -> Timeline' window
3. Select a GameObject and create a new Timeline asset
4. Add any track to the Timeline
5. Change the Layout of the Editor
6. Click 'Cancel' in the prompt
7. Observe the Editor

Actual results: Another duplicate prompt is shown (3 more times) followed by a 'Missing Default Layout'

Expected results: Layout change is canceled, no more prompts are shown

Reproducible with versions: 6000.0.82f1, 6000.2.0a7, 6000.3.23f1, 6000.5.10f1, 6000.6.0b10, 6000.7.0a5

Not reproducible with versions: 6000.2.0a6

Tested on (OS): Windows 11 Pro (25H2)

Notes:

• After 4 prompts, another prompt is thrown: "Missing Default Layout", asking to restart the Editor
  • Data may be lost as a result if 'Quit' is pressed