patch 8.2.4959: using NULL regexp program

Problem:    Using NULL regexp program.
Solution:   Check for regexp program becoming NULL in more places.

src/version.c

@@ -746,6 +746,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    4959,
 /**/
     4958,
 /**/