Fix a Pen tool regression where a new single-point layer doesn't get deleted but should

[c-mateo]

Issue #2503 was reintroduced in #2452 by the line 1928 in pen_tool.rs. This PR fixes it but please check the improvements done in #2452 are still working fine.

[Keavon]

@0SlowPoke0 can you please review this?

[Keavon]

@c-mateo please clarify what this regression is, since we can't seem to reproduce it in https://dev.graphite.rs.

[c-mateo]

As #2503 describes, a single anchor path can be created by:

• Selecting the pen tool
• Mouse down
• Mouse up
• Switch to another tool (with a shortcut or the button)

And this is not desired. The bug is present in https://editor.graphite.rs/

[Keavon]

The bug is present in https://editor.graphite.rs/

This is not a deployment of master.

[c-mateo]

I used to hunt bugs there. So, false alarm? And what's deployed there?

[Keavon]

Yes, always use dev not editor (prod) for finding bugs. Prod deploys https://github.com/GraphiteEditor/Graphite/releases/tag/latest-stable and you can also always use the Help > About Graphite... menu to view the commit hash and look up that commit for any deploy you're ever running.