updated for version 7.3.851

Problem:    Using an empty pattern with :sort silently continues when there is
            no previous search pattern.
Solution:   Give an error message.

src/version.c

@@ -728,6 +728,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    851,
 /**/
     850,
 /**/