updated for version 7.3.689

Problem:    MzScheme and Lua may use a NULL string.
Solution:   Use an empty string instead of NULL. (Yukihiro Nakadaira)

src/version.c

@@ -719,6 +719,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    689,
 /**/
     688,
 /**/