Clear ("x") button remains visible in the Entities Systems window search bar after deleting all query blocks

Steps to reproduce:

1. Create a new 3D URP project
2. Install com.unity.entities package
3. Go to Window > Entities > Systems
4. Click the "+" icon in the search bar and add any query block
5. RIght-click on the added block and Delete
6. Observe the "x" at the end of the Search bar

Actual results: The clear ("x") button is still displayed at the end of the search bar after the query block is deleted, even though the search bar is now empty and there is nothing left to clear (Clicking it has no effect)

Expected results: The clear ("x") button should be hidden once the last query block is removed

Reproducible with versions: 6000.5.3f1, 6000.6.0b2, 6000.7.0a2

Can’t test with versions: 6000.3.19f1 (query blocks not available)

Tested on (OS): Ubuntu 24.04, macOS 26.5

Notes:

• Same functionality works correctly in the Global Search window