Deleting an artboard doesn't update

[0HyperCube]

To reproduce:

• Create a new document with an artboard (checked by default in the new document dialogue)
• Select the artboard in the layer tree
• Press the delete key

Observe that the artboard is still displayed until the document is rerendered (e.g. by drawing a rectangle). This shouldn't happen.

Regression from #2265.

[prchoward]

I would like to take on this issue if possible. I am a senior cs major with some graphics programming experience with opengl and looking forward to making an OSS contribution

[Keavon]

Hi @prchoward, welcome! Yes, please give this a try. For a little extra context, this is the one regression that slipped through without being noticed when I made this refactor #2265. I was going to work on fixing it today since killing all the regressions ASAP is important, as part of the effort of making that refactor. Please take a shot at it, but be aware that if you don't have it solved shortly, I might fix it myself before you get to it. If that's the case, there are plenty of other options for issues to work on. But if you can save me the time of doing this fix, that'd be appreciated!