This error is caused by a corrupted version of Keyboard Maestro from a third party site.
Installing a clean copy from our site should normally resolve it.
https://download.keyboardmaestro.com/
Make sure you quit Keyboard Maestro Engine and Keyboard Maestro before installing the fresh copy.
Restarting your Mac is not normally required, but may be required. It is hard to know exactly what damage the corrupt third party version does.