Floating windows occasionally get "stuck" and are unable to be closed

[lethalbit]

This is annoying to reproduce, but i've hit it on multiple occasions, in this case with the Waveform View panel.

When the panel is undocked, either intentionally or accidentally when moving it around, it will float onto the desktop as a second window, once there it will occasionally get stuck, as in you can't move the window, nor close it anymore, you can however, resize it.

I'm unsure the exact cause, and sometimes by playing with the window enough you can get it unstuck, but I've not found a fully reproducible method. It could be related to #651? Seems like that would cause some of the weirdness i'm seeing.

This is as of fd3974e, and it's happened before then too.