Steps to reproduce the issue

install [4.0Alpha] with no sample data
Go to the admin console adn see the "sample data" module with a link called "Blog Sample data"
Click that link

Expected result

Something......

Actual result

a blue progress bar gets to 100% and a JS issue (from flying focus as ever)
Then the result of the ajax call to
http://0.0.0.0:8010/index.php?option=com_ajax&format=json&group=sampledata
results in

{"error":true,"code":0,"message":"Call to a member function save() on boolean"}

System information (as much as possible)

Unique ID 707d2b7806a60debd39e54bb17bfc8cf98c6de6f
PHP Version 7.1.11
DB Type mysqli
DB Version 5.7.20
CMS Version 4.0.0
Server OS Darwin 17.3.0

Additional comments