GtkCanvas and Testset Error

[nHackel]

Hello, we stumbled over an issue with our UI tests after migrating to Gtk4.jl. In the tests we are creating a complex GUI that features multiple GtkCanvases, which we then compare to expected images. With Gtk4.jl these tests fail with the Canvas not being initialized.

I've managed to reduce it to this MWE:

using Gtk4, Test

@testset begin
	c = GtkCanvas()
	win = GtkWindow(c)
	# show(win) # doesn't work with or without show
	getgc(c)
end

I think the tests within Gtk4.jl works somewhat similar (at least they create Canvases within a testset), I'm not sure exactly what I'm missing to get this to work