fix [3408713] Dialog window invisible sometimes

weak pointer comparison operators were implemented wrong,
they were using the internal "unsafe" pointer. We could end up
with two "equal" weak pointer pointing to different objects.

this caused KeyedVector keyed by weak pointer to work incorrectly, in
turn causing a window that just got added to a list to be immediately
removed.

Change-Id: Ib191010c39aafa9229109e4211f6c3b2b2f9696d