Undo Shortcut "Ctrl+Z" doesn't work on split Scene Editor

Release Type: Official Release

Version: Both 3.1 Latest Beta & 3.0 Latest Version

Platform(s): Window10 1809

Describe the bug Undo Shortcut "Ctrl+Z" doesn't work on split Scene Editor

To Reproduce Steps to reproduce the behavior:

1. Set the Scene Editor to floating status;
2. Do something in the Scene Editor;
3. Press the Undo Shortcut "Ctrl+Z",whatever the Editor is Focus or not;

Expected behavior The operation in Scene Editor can be Undo.