MCreator issue tracker has been migrated to GitHub.
Existing tickets have been migrated to GitHub. Please open new tickets on the GitHub tracker instead. If you do not have a GitHub account, all feature requests and bug reports from forums are still considered and checked by the maintainers.
I have imported your workspace and it worked. Try to import your exported workspace back and it might fix this error. Keep in mind that we will fix most of these types of errors in 1.8.1.