How to reproduce:
1. Open attached project "SelectGameObjectBug.zip" and scene "SampleScene"
2. In Hierarchy window, select "Controller" object
3. In Inspector window, enter "Select GameObject" window by pressing on the circle of "The Game Object" variable
4. In "Select GameObject" window, go in Assets tab
5. While the search field is active and empty, press left and right keys

Expected result: the left/right keys switch between "Select GameObject" objects
Actual result: the left/right keys are still used in the search tab, even though there is no text

Reproducible with: 2018.2.0a2, 2018.2.8f1, 2018.3.0b1
Not reproducible with: 2017.1.5f1, 2017.4.11f1, 2018.2.0a1