Cursor remains in text fields when clicking on some buttons or scroll lists

The bug

Clicking on a button or on a scroll list entry in 1.12.2 caused the cursor from a currently focused text field to be removed, this is not the case for all buttons and scroll lists anymore in the latest versions. Now for some the cursor remains in the text field but pressing keys won't type in it since it is not focused.

Affected GUIs and GUI elements

• Superflat customization: Clicking on preset
• Command block GUI: Toggling output tracking

How to reproduce

1. Open the command block GUI
2. Click in the command input text field
   → The cursor is blinking
3. Click on the button to toggle output tracking
   → The cursor is still in the text field even though it is not focused anymore