Preference dialog does not render properly if opened on a monitor other than the one Gummi initially launched on

[CorvetteCole]

Describe the bug
If you attempt to view the preferences dialog after dragging Gummi to a new monitor, it will not render.

To Reproduce
Steps to reproduce the behavior:

1. Open Gummi on primary monitor
2. Open preference dialog, observe functionality, close
3. Move Gummi to secondary monitor
4. Open preference dialog, observe empty dialog

System:

• OS: Arch Linux
• DE: Gnome
• Compositor: Mutter 43.1
• Wayland
• Gummi version 0.8.3

Other
Notice empty dialog box in middle.

[cmahte]

Works fine on Ubuntu 20.04 using gummi 0.8.1 that comes with ubuntu.

However, after I move the gummi window, the preference dialog doesn't center on the new location but pops where it was the first time. A lot of popups across many programs have this behavior though. not a gummi feature.