patch 8.0.1403: using freed buffer in grep command

Problem:    Using freed buffer in grep command. (gy741, Dominique Pelle)
Solution:   Lock the dummy buffer to avoid autocommands wiping it out.

src/version.c

@@ -771,6 +771,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1403,
 /**/
     1402,
 /**/