[macOS] Typing diacritical mark fails when changing to other window

When entering a diacritical mark (e.g. Option+E) and changing focus to another window the original textedit widget is left in bad input mode.

Steps to reproduce the issue:
1. Switch macOS keyboard layout to US
2. Run attached test application
3. Press Option+E
4. Press CMD+E
5. Press e

Expected outcome:
New window is opened and the ´ mark typed in the original window is handled sensibly

Actual outcome:
New window is opened and the ´ mark is left in the original window. é is typed in the newly opened window. ´ can't be cleared in the original window. If 'e' isn't typed to the new window the original window can't be focused.