Right click on treeview fires Gdk-CRITICAL **: xdg_popup_configure

Hi there!

If I open meld through the terminal (meld .), all right-click on the treeview will fire the following exception:

2018-02-07 23:02:53,965 CRITICAL Gtk: 
(meld:17823): Gdk-CRITICAL **: xdg_popup_configure: assertion 'impl->transient_for' failed

This does not crash the application, but each right click on the list throws this error.

Using GNOME Shell 3.26.2 on Arch Linux.