Block extensions only work if they are alphabetically sorted after editor

Describe the bug Block extensions with plugin folders that are alphabetically sorted before editor don't work.

To Reproduce Steps to reproduce the behavior:

1. Copy a block extension example to your plugins folder
2. Rename the block extension folder to something that is sorted before editor
3. Open the panel in your browser and look at the console. The error above should appear.

Expected behavior The block extension should work

Kirby Version 3.5.0

Console output Uncaught ReferenceError: editor is not defined

Desktop (please complete the following information):

• OS: macOS
• Browser: Chrome
• Version: 87