bug#32975: Emacs 26.1; GTK Warnings

[Eli Zaretskii]

> From: Tjernlund <tjernlund@tjernlund.se>
> Date: Sun, 07 Oct 2018 20:19:26 +0200
> 
> Setting background-color like so(in my .emacs files):
> (setq default-frame-alist '((background-color . "#333333") (foreground-color 
> . "White") (cursor-color . "White")))
> 
> Prints these GTK warnings:
> (emacs-26:9664): Gtk-CRITICAL **: gtk_widget_get_parent: assertion 
> 'GTK_IS_WIDGET (widget)' failed

Please tell your GTK version (and preferably all the other
information collected by "M-x report-emacs-bug RET").

Thanks.

P.S. Do I understand correctly that these messages are emitted only
for that combination of colors?