Unexpected error when deleting project with Business Process

For a simple project there is an Unexpected error when:

1. create a project
2. add asset -> Business Process
3. save the process (happens both for valid and invalid processes)
4. go back to the project
5. click Delete project
6. Unexpected error appears

Uncaught exception: (TypeError) : Cannot read property 'offsetWidth' of null | Uncaught exception: (TypeError) : Cannot read property 'offsetWidth' of null