Search field loses its value when a column is sorted

[m4theushw]

What you were expecting:
The value of the search field should be kept when sorting.

What happened instead:
The search field loses its value when a column is sorted.

Steps to reproduce:
Open this sandbox
Type something into the search field
Click the "Title" column to sort

Environment

• React-admin version: 3.0.0-beta.3
• Last version that did not exhibit the issue: https://marmelab.com/react-admin-demo
• React version: 16.8.6
• Browser: Google Chrome 77.0.3865.120

[djhi]

Thanks for the report!

[fzaninotto]

Fixed by #3887