After updateing my J4-alpha-9-dev to -10-def I get the following error: "An error has occurred.
0 Class 'JEventDispatcher' not found"

Steps to reproduce the issue

1. Open system>manage>plugins (or any of the moduls)
2. Select any of the listed plugins an go into it.
3. Do a "save" || "save2exit" || "close"
   4 The error-message occurred.

Expected result

Return without error-message to the plugins-listview.

Actual result

5 Error: Class 'JEventDispatcher' not found

System information (as much as possible)

J4-alpha-10-dev-full: Completely new installed and nothing ever changed.
J4-alpha-10-dev-update from alpha-9: The same error happens.

Additional comments

When doing a page-reload the listview is shown.