The actual root of this issue is caused by the underlying call to reactpy.utils.string_to_reactpy, which will fail if called with an empty string.
This was discovered in the context of refactoring reactpy-django to work with the latest reactpy core pre-release. The reactpy-django package had its own implementation of pyscript_component, but in switching that one out for the one officially provided by reactpy core this issue was revealed.

See the code here: