Composition Entities delete failed when the Master entity extends BaseStringIdEntity

I did a demo followed the manual-5.8.3 “Editing Composite Entities”,and i found if i create the
Master Entity extends BaseStringIdEntity,then i could create and edit the “Master-Detail” entities well,
but when delete ,i got the Exception “The state field path ‘’ cannot be resolved to a valid type.”
(e is the detail entity,username is the master entity’s id).
If let Master entity extends StandardEntity,it work well.
I use Studio 2.0.6 ,platform 6.0.9.
Wish you could help.

Best Regards.

Thank you for reporting the problem.
We will fix it in one of future platform releases.

the problem is fixed in the platform version 6.1.2.