patch 8.1.0098: segfault when pattern with \z() is very slow

Problem:    Segfault when pattern with \z() is very slow.
Solution:   Check for NULL regprog.  Add "nfa_fail" to test_override() to be
            able to test this.  Fix that 'searchhl' resets called_emsg.
diff --git a/src/version.c b/src/version.c
index f440ff9..5cf6882 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    98,
+/**/
     97,
 /**/
     96,