There was an old bug where a wand of secret door detection was identified
even though it didn't find anything.
It was unconfirmed, but I had no trouble confirming it. It happened because
the wand worked on squares that were couldsee() but which (because they weren't
lit) you couldn't actually see. The wand would detect the secret corridor and
then not display it because it was out of sight.
I fixed it to display the corridor, in sight or not (I could have had it not
detect anything, but the wand is fairly weak already.)
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