halos now cause a MouseLeave event to be sent to its target

In 5.1, I could have a halo on my morph and let it retain keyboard focus.

Now, in 5.2, invoking halos sends a MouseLeave event, which my app
responds to by removing keyboard focus.

Halos are *around* the morph, the mouse pointer is still *in* the
(bounds of) morph.  I don't think their invocation should cause this
event to be signaled...   what do you think?