Asmodeus' cold magic attack when hero is resistant

Asmodeus kept using the cold magic attack when hero was cold resistant.
The distance magic attack already considered hero resistances, so
use the same logic for the close-up magic attack.

src/mcastu.c

@@ -221,7 +221,8 @@ castmu(
     }
 
     /* monster unable to cast spells? */
-    if (mtmp->mcan || mtmp->mspec_used || !ml) {
+    if (mtmp->mcan || mtmp->mspec_used || !ml
+        || m_seenres(mtmp, cvt_adtyp_to_mseenres(mattk->adtyp))) {
         cursetxt(mtmp, is_undirected_spell(mattk->adtyp, spellnum));
         return M_ATTK_MISS;
     }