When setting a QMenu to a QAction a bizarre dot appears

when creating an empty QMenu and adding it to an QAction a bizarre black dot appears when the mouse's cursor move on it.

To reproduce the bug open the visual studio project given in the zip file then follow these steps:

1) Start a debug session

2) wait for start page Google to load
3) click on the star (see image below) to add to favorites
 
4) go to "Navigation" menu then "Favoris". You should see this:

5) then move the mouse on "Google" then you will see the black dot appearing

More clearly here: 

Note that:

• the dot disappears if you add some actions to the menu. 
• if you make some other coding manipulations with this menu without adding an action to it you will see other dots appearing (when rightclicking on it for example).

The lines of my code which makes this bug appears are the following: