Stuck notes when menu is open

[josh-audio]

Found by @DomClark. Closely related to #1755.

Steps to reproduce:

1. Open TripleOscillator.
2. Open the edit menu.
3. Press some keys on the keyboard to play notes in TripleOscillator.

This causes the notes to stick.

Reproduced on LMMS 1.2.0 RC8 and master (as of this build) on Windows 10.

[PhysSong]

#3654 is also related because QMenu blocks key events in both cases. There are some exceptions like forwarding unhandled key press event to the menu bar. This causes only key press events to be forwarded to the main window, not key release events.

[JohannesLorenz]

I just tested exactly what @SecondFlight mentioned on your branch. The problem still seems to exist. Am I testing right? -> Sorry, I wanted to post this to the PR, not here

[musikBear]

Cant repro. on win10 1.2.1:

immediately i press a key, the Edit-menu closes (?)
Are you referring to an other 'edit-menu' ?

[JohannesLorenz]

@musikBear Thanks for trying. Did you use the stable-1.2 branch or this PR's branch ("qmenufix")?

I mean exactly the edit menu you show in the picture. It does not close for me if I use the keyboard to play notes.

[musikBear]

@JohannesLorenz As i wrote win10 off. stable 1.2.1

I also have a rc7.263, the behaviour is the same. The menu closes as i press a note on the preset-keyboard.
So i also tried with the piano-roll kb, and that gave same result. Menu closes if a key is pressed, witch also is expected. The menu-dropdown is not modal, and should shut at any event in UI

I guess this bug would be for an external HW midi-keyboard. Dont have one