Can't issue actions like Cleave by Grid with keyboard shortcuts while 3D Preview window focused

[thekovic]

Describe the bug
Commands like Snap Grid to Object and Cleave by Grid can't be issued with keyboard shortcuts while having focus on the 3D Preview window. I have to keep clicking back into the main window to issue those.

To Reproduce
Steps to reproduce the behavior:

1. Open 3D Preview.
2. Press Alt+C to issue Cleave by Grid.
3. Nothing happens.

Expected behavior
Command should be executed and any selected surface/sector should get cleaved.