another compiler warning

src/zap.c

@@ -2026,7 +2026,7 @@ dozap()
 	check_unpaid(obj);
 
 	/* zappable addition done by GAN 11/03/86 */
-	if(!zappable(obj)) pline(nothing_happens);
+	if(!zappable(obj)) pline("%s", nothing_happens);
 	else if(obj->cursed && !rn2(WAND_BACKFIRE_CHANCE)) {
 		backfire(obj);	/* the wand blows up in your face! */
 		exercise(A_STR, FALSE);