* Don't do anything in MouseIdle if we're not dragging a message.

This especially avoid bringing tracker windows up to front when staying idle
over a tracker window while holding down a button. This could happen when
hovering while still holding a scroll thumb of another overlapping window.

Fixes regression #7829 introduced in r41892

* Also properly reinitialise the cached dragMessage on B_EXITED_VIEW, 
otherwise it would still think it is dragging and thus still pass through my
above fix.

I'd like to cleanup the drag message caching mechanism as it's not 
pretty in my opinion. Possibly even adding it to BView.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@42441 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/kits/tracker/ContainerWindow.cpp

@@ -3790,7 +3790,7 @@ BContainerWindow::SaveWindowState(BMessage &message) const
 status_t
 BContainerWindow::DragStart(const BMessage *incoming)
 {
-	if (!incoming)
+	if (incoming == NULL)
 		return B_ERROR;
 
 	//	if already dragging, or