Copy-Paste does not always work in node editor on Windows

[MathemanFlo]

ArmorPaint version: ArmorPaint.org - v0.9 (2022-04-01) - 9ecb690 Windows - Direct3D11

Issue description: Copy for nodes does not always work.

Steps to reproduce:

1. Open the default material
2. right click on the default RGB node
3. Select copy
4. Click somewhere else on the canvas
5. Right click -> can not paste

It is weird, adding a new node and copy/paste it works depending on whether ctrl+c or right click + copy was chosen.

[MathemanFlo]

I took a quick look at it and it seems that UINodes.render is not always called and thus the copy/paste operation is not always performed.