nautilus-window: make sure active slot is closed last

When destroying window and closing all slots, the closing
of the active slot will trigger activation of next free slot,
we don't want to be activating slots as part of
'closing all slots' logic.

Fixes bug 741952
Revert "nautilus-window: Check for valid location entry widget"

This reverts commit 8acef3c776f2ef4f5dac788ed81f7e2d1f504026.

https://bugzilla.gnome.org/show_bug.cgi?id=741952