[shell32] startmenu-drawing & systray-drawing is broken cross-dependently

r71529 gcc dbg is affected (since more than a year the very same way)

good-path:
1.) click on the startmenu button.
2.) make sure you don't hover over something that expands
3.) click on the desktop to close the start-menu
4.) when you click start-menu-button again, start-menu is drawn fine & systray is drawn fine too.

bad-path:
1.) click on the startmenu button.
2.) make sure you hover over something that expands
3.) click on the desktop to close the start-menu
4.) when you click start-menu-button again,
start-menu top-most entry is not drawn initially
After a second when it is drawn finally, the systray-icons are drawn blank

Of course only a minor glitch, but a new reactOS user will stumble above this within the first minutes of usage for sure.
see also attached video.webm

cc smiley, hbelusca, gigaherz