The bug

If you type something into a sign and then use the arrow keys to edit the text, the cursor indicating where you are within the text disappears.

What I expected to happen

The cursor should move when the arrow keys are pressed to indicate what part of the sign text is being edited.

What actually happened

The cursor disappears and there is no visual indication of where you are within the sign text.

To reproduce

1. Place a sign in any world and add text
2. Use arrow keys to navigate back in the text
   →  The cursor disappears until you return to the end of the text

See attached video and image below.