Set Input Mode (UI Only/Game Only/Game and UI) Does not give an error when there is not a target connected (player controller)

When using a node that sets the input mode for the game, the input node will not take effect unless there is a player controller specified. However, the node does not give any warning of this.

1. Open the Editor
2. Open the level blueprint
3. Add an 'F' key event
4. Drag off of the pressed execution pin and type "Set Input Mode UI Only"
5. Save and compile
6. Notice there is no warning
7. Play in Editor
8. Press the 'F' key
9. Notice that the Screen does not switch input modes (the screen continues to follow the mouse)
10. Stop PIE
11. Open the Level blueprint
12. Drag off of the Target pin of the "Set Input Mode UI only" node and type "Player Controller"
13. Save and Compile
14. Click PIE
15. Click the screen and move the mouse around (Screen should be tracking the mouse)
16. Press the 'F' Key
17. Notice the Screen stops tracking the mouse (expected)

Expected: The node should give a warning when there is not a target (Player controller) given
Result: The blueprint compiles (when there is no player controller setup as the target) and given no warning that the node will not function

Set Game Mode Focus doesn't require controller ref