Gdk issue with tooltips/arrows(?)

Steps to reproduce

1. Install Racket on Ubuntu 17.10 and open DrRacket.

2. Enter the following in the definitions window:

#lang racket

(modulo 10 2)

3. Mouse over modulo

Instead of the arrow back to #lang racket and a tool tip appearing, the arrow appears and disapears in rapid succession, it seems like the window manager focuses and unfocuses on DrRacket each time this happens, and if you launched DrRacket from the terminal you see the following repeated each time the arrow/tool tip is drawn and disappears:

Gdk-Message: Window 0x5627860bc4c0 is a temporary window without parent, application will not be able to position it on screen.

This is especially troublesome when in a #lang that makes frequent use of tool tips (e.g. Typed Racket, etc).

I have observed this with the 6.10.1 release and with a built-from-source install.

Reproduce the issue in DrRacket on Ubuntu 17.10 using the provided #lang racket and modulo example, then observe the tooltip and arrow behavior alongside the repeated Gdk warning. Done means hovering over modulo keeps the arrow and tooltip stable without repeated focus changes or warnings.