Fold invisible glyph unmapping into single function

src/hack.c

@@ -1635,10 +1635,7 @@ domove()
         }
         return;
     }
-    if (glyph_is_invisible(levl[x][y].glyph)) {
-        unmap_object(x, y);
-        newsym(x, y);
-    }
+    (void) unmap_invisible(x, y);
     /* not attacking an animal, so we try to move */
     if ((u.dx || u.dy) && u.usteed && stucksteed(FALSE)) {
         nomul(0);