shell32/autocomplete: Check the edit control in ResetEnumerator instead of whether the object is initialized.

An autocomplete object can be destroyed and detached from the edit control and
still survive, if there are still references to it (even though it's useless).
Signed-off-by: Gabriel Ivăncescu <gabrielopcode@gmail.com>
Signed-off-by: Huw Davies <huw@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>