existing itemstore not preserved by overrider

[shawkins]

Bug Report

What did you do?

When using ControllerConfigurationOverrider on a controller that has an customized itemStore, it is nulled out.

What did you expect to see?

The original should be preserved.

[csviri]

@shawkins can you elaborate more please, how this happens exactly, you customize the event store with @ControllerConfiguration and then using @ControllerConfigurationOverrider without setting one, then it is nulled out?