B12009 invisible nymph preposition consistency

<Someone> reported the messages "It seduces you and you take off your
robe. She stole a burnt +0 robe."  I noticed the 2 cases here only dealt
with blindness, not seeing the nymph in general.  Also, one case forced
"She", the other "It".  Now they both say "She", which is consistent with
the preposition in the 2nd message.  We'll continue to the assume the
gender of the seducer is obvious, even when unseen.

src/steal.c

@@ -357,6 +357,7 @@ gotobj:
 		    } else {
 			int curssv = otmp->cursed;
 			int slowly;
+			boolean seen = canspotmon(mtmp);
 
 			otmp->cursed = 0;
 			/* can't charm you without first waking you */
@@ -364,13 +365,13 @@ gotobj:
 			slowly = (armordelay >= 1 || multi < 0);
 			if(flags.female)
 			    pline("%s charms you.  You gladly %s your %s.",
-				  Blind ? "She" : Monnam(mtmp),
+				  !seen ? "She" : Monnam(mtmp),
 				  curssv ? "let her take" :
 				  slowly ? "start removing" : "hand over",
 				  equipname(otmp));
 			else
 			    pline("%s seduces you and %s off your %s.",
-				  Blind ? "It" : Adjmonnam(mtmp, "beautiful"),
+				  !seen ? "She" : Adjmonnam(mtmp, "beautiful"),
 				  curssv ? "helps you to take" :
 				  slowly ? "you start taking" : "you take",
 				  equipname(otmp));