updated for version 7.3.1143
Problem:    When mapping NUL it is displayed as an X.
Solution:   Check for KS_ZERO instead of K_ZERO. (Yasuhiro Matsumoto)
diff --git a/src/message.c b/src/message.c
index b574df6..8330ef7 100644
--- a/src/message.c
+++ b/src/message.c
@@ -1577,7 +1577,7 @@
 	{
 	    c = TO_SPECIAL(str[1], str[2]);
 	    str += 2;
-	    if (c == K_ZERO)	/* display <Nul> as ^@ */
+	    if (c == KS_ZERO)	/* display <Nul> as ^@ or <Nul> */
 		c = NUL;
 	}
 	if (IS_SPECIAL(c) || modifiers)	/* special key */